FAQ
Here you will find a selection of frequently asked questions with regard to Passive Houses.
GENERAL QUESTIONS
Passive Houses
iPHA
Education
Literature
The PHPP
Building and component certification
TECHNICAL QUESTIONS
Airtightness measurements
Doors and windows
Climate data
Ducting
Insulation
Non-Residential Buildings
Heating in a Passive House
Ventilation
Centralised vacuum cleaning system
EnerPHit retrofitting
These FAQs are brought to you in part by PassREg and EuroPHit, co-funded within the European Commissions's Intelligent Energy Europe programme (IEE).
General questions
Passive Houses
Are there different Passive House Standards for different climates?
Whether in Siberia or Southern Spain, one of the beauties of the Passive House Standard is its consistency (see the Passive House criteria).
These criteria are functional and based on the ability to heat the house solely through the supply air. They are not climate dependent. Instead, the design of each Passive House building must be adapted to the particular climate in which it will be built, meaning that these criteria may sometimes be more or less difficult to fulfil. A Passive House in Siberia, for example, would likely require better thermal protection than a Passive House in Southern Spain.
Isn't Passive House still in the research and development phase?
Yes and No. The first ever Passive House prototype was built in Darmstadt in 1991. Since then, Passive House has rapidly increased in popularity. With over 25,000 units certified according to the strict Passive House Institute certification criteria representing a total floor area of almost 2,350,000 m² TFA (as of 01/2020). Many of these quality-assured examples are included in the Passive House Database, which documents more than 4,900 Passive House buildings.
That being said, the Passive House Institute is constantly working to further evolve and improve upon the Passive House Standard. This means research into improving the energy efficiency of all kinds of buildings including swimming pools, high-rises, grocery stores, etc. As well as constantly working to improve the programs and tools provided by the Passive House Institute, that make it easier and easier to implement the Passive House Standard.
Is the Passive House Standard only applicable to houses?
No, Passive House is a very versatile concept that can form the basis for the design of any type of building. Schools, banks, apartment and office buildings are only some examples of Passive House certified buildings. For both the non-residential and residential Passive House certification criteria, please see the Passive House criteria. For more information on Passive House certified projects go to our Passive House Database or read more on Passipedia
Can a building really stay warm without a conventional heating or cooling system?
Time and again, Passive House certified buildings have proven that it is possible to build structures requiring so little energy, that conventional heating and cooling systems are rendered unnecessary. During cold periods, the small amount of heat that can be added to incoming fresh air through a ventilation system is sufficient to keep a Passive House at a comfortable temperature. During warmer periods, strategic shading and aeration is typically enough to keep a Passive House comfortably cool, although in warm, humid climates, some type of small scale air conditioning may be required. Measurements in Passive House subdivisions have proven that Passive Houses keep energy requirements consistently and predictably low: the expected consumption agrees well with average actual consumption, even given a great variety of occupant habits and lifestyles.
To what extent is the construction of Passive House buildings worthwhile in terms of climate protection?
Currently, the building sector accounts for approximately 1/3 of global CO2 emissions. To reduce these emissions and meet urgent climate goals, it is necessary to both improve building energy efficiency and implement renewable energy. Passive House buildings are thus a perfect solution. An enormous amount of energy can be saved with Passive House buildings in comparison to the operation of conventional buildings. Up to up to 90% compared with typical building stock and over 75% compared with average new builds. In addition, on account of their minimal energy consumption, the demand in Passive House buildings can easily be supplied by renewable energy.
How do I know if a company that claims to build Passive Houses is legitimate?
A company with legitimate Passive House experience should be able to show that they employ Passive House Institute Certified Passive House Designers/Consultants (as listed here) or that they have built Passive House Institute Certified Passive Houses (please note that projects listed on the Passive House Database, while not always certified, also undergo a basic plausibility check). For more information on certification, click here. All Certified Passive Houses come with certification papers, which the company should be able to show for past projects. If a company has none of the above, it should at least be able to show the verification page of PHPPs (the energy balance design tool for Passive Houses) for past projects. This verification page should then show that the building has met the Passive House criteria.
Aren't Passive Houses expensive?
Passive Houses not only save money over the long term, especially in light of rising energy costs, but are surprisingly affordable to begin with. The investment in higher quality building components required by the Passive House standard is mitigated by the elimination of expensive heating and cooling systems. The financial support increasingly available in many countries makes building a Passive House all the more feasible.
Even so, Passive Houses do cost more upfront than their conventional counterparts. On average, someone building a Passive House in Germany might expect to spend between 3-8% more, and this cost differential is likely more in countries where Passive House components are not yet readily available. As the number of Passive House suitable components on the market increases, however, prices in these other countries will drop. Financial support for Passive Houses, as currently available in a number of countries, further reduces their cost. In this light then, building a Passive House may even be more affordable over the long term than building a conventional home.
in fact, in a 2016 German study on publicly funded housing construction projects in Hamburg, Germany, it was found that the construction costs for the Passive House standard were the most affordable of the possible construction options.
Ask your regional or national authority for details on support for Passive Houses in your area. More information on aid programmes can be found under the Legislation & Funding section of this website.
Can you open windows in a Passive House?
Passive House occupants may open windows whenever they want. The beauty of Passive House design, however, is that they won't have to. A Passive House is continuously supplied with fresh air via the ventilation system, which does a far better job of consistently bringing fresh air in than simply opening the windows ever could. This has advantages: unlike just opening the windows, fine filters in the ventilation system keep dirt and pollen out- a blessing for those who suffer from allergies and respiratory problems. Indoor air quality is always excellent, even when occupants are away and/or windows are never opened. Of course, as with all houses, if windows are left open for longer periods with extreme outdoor temperatures, the inside air temperature will be affected and energy consumption for heating/cooling will increase.
People often express reservations about the need for a ventilation system: are there problems with bacteria, noise and drafts?
The ventilation system in a Passive House is a fresh air supply system, not an air conditioning system that recirculates inside air. Bacterial growth is only a problem in poorly maintained recirculating air systems. The fan and valve noises resulting from the ventilation system are almost completely eliminated by sound control measures such as vibration isolation mounts, low airspeed and acoustic lining in ducts. Jet nozzles guide incoming air along the ceiling, where it uniformly diffuses throughout the room at velocities that are barely perceptible.
How does Passivhaus construction prevent moisture damage?
In Passive Houses, airtight construction and thick insulation maintain even indoor temperatures at around 20°C (dependent on user preference) throughout, thus preventing condensation and mould growth. Airtight construction also prevents leaks through which moist air can enter the building envelope.
Isn't a Passive House a complicated, high-tech building?
Not at all! More than anything, a Passive House utilises higher quality versions of the same building concepts and components that are utilised in typical buildings. The ventilation system, not common in conventional buildings, is user-friendly and easy to operate with fewer controls than a typical television. Passive House technology is so simple, there's no need to hire someone to perform annual air filter changes; you can do it yourself.
iPHA
How can I change the information in my Member Profile and on the member search?
You can update your information as well as your entry in the iPHA member search by signing into the Member Area with the user name/password (provided in your membership confirmation email) and clicking "Update Profile". To change your user name and/or password, simply edit the information in the Passipedia/iPHA login section. Here you can also add a description of what you do, a company logo if you have an organisational membership, and add users in accordance with the number of access keys that come with your membership.
I forgot my iPHA Password, what do I do?
To reset your password, please click "reset password" on the iPHA Member Area login site. Once logged in, you can change your password and user name in your member profile, along with your other profile information. Please note: the password for the iPHA Member Area is the same as the password for Passipedia.
My company is listed as an iPHA member. Can multiple staff have access to the iPHA forum, Passipedia and the iPHA Member Area?
Those with an organisational iPHA membership can add users in accordance with the number of access keys that come with their membership. The administrator of the membership account (the person/email address listed as the iPHA Contact in the member profile) can update account information and the organisation's entry in the iPHA member search by signing into the Member Area with the user name/password (provided in the membership confirmation email) and clicking "Update Profile". In the profile, there is a section called "Passipedia/iPHA login & password". Here you will see the number of access keys/users available to the account as well as which are assigned and how many are left. Each available access key can be assigned to one user/email address and gives the user access to all iPHA benefits but does not allow that user to change the organisation's profile or give out other access keys. The administrator of each account can easily delete users and reassign them.
Education
What is the difference between a Passive House Designer and a Passive House Consultant?
The difference between Passive House Institute certified Designers and Consultants depends on your background. Designers come from highly relevant fields and must somehow show proof of their previous knowledge through their degree etc, in order to get the Designer label. Consultants, on the other hand, can come from any background. See the FAQ from the training website for more details.
How can I become an internationally recognised, Certified Passive House Designer?
Since the development of the Passive House Designer scheme in 2006, some 1500 professionals have earned the international designation of “Certified Passive House Designer” in one of two ways: by taking the International Passive House Designer exam with any of the examination bodies worldwide, or, better yet, through the submission of a report documenting a Passive House building, planned by the applicant and certified by a PHI accredited Passive House Building Certifier. Please refer to our education section for more information.
See the list of PHI accredited course providers
What is the CEPH Course?
Course providers worldwide may choose to use any materials they like in preparing their students for the international Passive House Designer exam and indeed, those wishing to take the exam may prepare themselves through self-study. For interested course providers, however, PHI offers its Passive House Designer course material, available in a variety of languages. This material is based on the CEPH course materials, which resulted from an EU-funded project by the same name involving several partners. For more information, see the education section.
Go back to FAQ index
Do all the PHI accredited examination bodies offer the same course and how do I know which ones offer the best quality training?
Not all course providers listed as such use the same course or course materials to prepare their students for the Passive House Designer exam. All Certified Passive House Designer courses offering PHI's material, based on the original CEPH course materials (see above), however, should follow the same format. Course providers using this material may add more slides / information and adapt the focus of the lessons in order to take into account local conditions such as construction methods and traditions, climatic conditions, and legal standards. While we can vouch for the quality of our material, we do not know what individual course providers who use it make of it. We therefore recommend that you ask the course providers the following questions:
- How many days does the course last and what aspects does it cover? (The course material distributed by PHI is set up to be a 10 day course covering Passive House basics, thermal envelope, ventilation, heating, PHPP, cost-effectiveness, renovation and quality assurance)
- What is your pass rate? (All exams will be graded by the Passive House Institute so a high pass rate really is a good indicator of the quality of the training offered by a course provider rather than of their goodwill when it comes to grading)
Literature
Have the “Protokollbänder” – Passive House Institute’s series of Passive House specific research findings, been translated into English?
iPHA has decided that translating each single volume cover to cover wouldn't make much sense. Although they all contain a lot of extremely valuable information, some of it is either outdated or applies to Germany or the German/Central European climate only and therefore shouldn't be translated directly. Instead, iPHA is collecting the most important articles and excerpts, updating and adapting them as required, and then making them available through Passipedia. Of course, this can't happen overnight, but we are working hard and Passipedia is continuously growing. In fact, many of the articles in the iPHA Member Area are from these "Protokollbänder".
See list of all Protokollbänder. Those that wish to order the Conference Proceedings, the German originals of the "Protokollbänder" or any other Passive House Institute literature (in German unless otherwise stated) may do so here.
Are the Conference Proceedings from each of the International Passive House Conferences available on Passipedia?
The Conference Proceedings of the last five International Passive House Conferences are available in English. The most significant findings from this series are currently being posted on Passipedia.
See list of all Conference Proceedings. Those that wish to order the Conference Proceedings, the German originals of the "Protokollbänder" or any other Passive House Institute literature (in German unless otherwise stated) may do so here.
The PHPP
How do I register to receive PHPP updates?
Even if you didn't buy your copy of the PHPP directly from the Passive House Institute, all you need to do to register for updates is fill out the registration form at the front of the PHPP handbook and fax it in.
Can you also use PHPP for calculating existing buildings that consume a lot of energy?
Yes, you can. On that case two things are important: the frequency of overheating result is incorrect and the heating load result is incorrect (both work only for very low energy buildings).
Read more about PHPP on Passipedia
Can standards other than ISO be used as the basis for component values entered into the PHPP?
No. The calculations carried out by other bodies are often based on different methods and thus lead to different results. In order to provide for reliable and comparable results, all values entered into the PHPP must therefore be based on ISO standards.
Read more about PHPP on Passipedia
Does one need simulations in addition to the Passive House Planning Package (PHPP)?
Generally, one has to be careful with simulations as they are only as accurate as the data you use to begin with, leaving a lot of room for error. The seemingly exact results they give can be misleading and the PHPP is certainly more fool-proof in this sense. In terms of hygrothermal simulations, once proven build-ups for any particular climate are known, such simulations are typically unnecessary and don't need to be done for each repeated use of the same construction type. For overheating, cooling, and dehumidification - areas that play a role in your locale, PHPP Version 8 has been calibrated using dynamic simulations. If, in the end, you want to use dynamic simulations, there are a variety of programs from which to choose from on the market, although they are all far more expensive than the PHPP.
Certification
Who is authorised to certify Passive Houses?
Any of the growing number of Passive House Institute accredited Building Certifiers are authorised to certify worldwide in the Passive House Institute/Wolfgang Feist's name.
Who accredits Passive House Building Certifiers?
The Passive House Institute is the only entity with the authority to train and certify Passive House Certifiers. There are currently over 30 certifiers worldwide, all accredited to certify in the Passive House Institute/Wolfgang Feist's name. These building certifiers are authorised to freely certify anywhere in the world according to Passive House Institute standards.
What does the certification process entail?
The planning of a Passive House building and, indeed, it's certification, is based on the PHPP or Passive House Planning Package. This excel based tool is perhaps the most accurate energy balance design tool on the market and study upon study has shown its results to be very much in line with both incredibly tedious dynamic simulations and with actual monitoring results (see Passipedia for more information).
For certification, the building plans, regional climate data set for the building's location, and performance values of the components used (windows, ventilation, etc) must be entered into the PHPP. The certifier then checks this completed PHPP for correctness. If data is missing or cannot be supported with evidence, the certifier is obligated to request this information. With the PHPP, the certifier can see if the building, as planned and with the values provided, is a certifiable Passive House. If not, the certifier may offer suggestions for how to improve the design while still in the planning phase, which is a great advantage - both heightening quality assurance and helping to avoid costly errors. The only aspect of certification that must actually be done on-site is the airtightness test, but this must be carried out by an independent third party (not the certifier).
When all is said and done, the construction site manager must sign that the building was built exactly as entered into the PHPP before any certification is awarded. If the building was not built as planned and there were anomalies during construction, this must be disclosed and the certifier will then take this into account in the certification calculations.
Go back to FAQ index
How can Passive House be both “open source” and at the same time a matter of contractual certification?
The Passive House is a freely accessible concept. You do not need any certificate to build one. Yet for those who would like to make use of the service, PHI, also through its accredited Building Certifiers worldwide, offers to check your plans to see whether they meet the Passive House Standard. This is not mandatory, but it may make for a more trusting relationship between you and your client. We stand with our reputation behind the “Certified Passive House” label.
This also explains why there are some 30,000 built Passive House Buildings in Europe, of which some 1,600 are certified. That is a huge number - and it's sufficient proof that the concept is working. The fact remains though: a Passive House building needn’t be certified to be a Passive House.
This said, we prefer to keep Passive House 'open source' and don't agree with the position that “more control is needed”. A paper issued by the Passivhaus Trust in the UK highlights this nicely. The claim that your building is a “Passive House” is a very serious one indeed. The Standard, open to all, is well defined; if your project fails to live up to your claims, you may find yourself in a difficult situation. Certification thus helps the designer to avoid this predicament and stands as a recognizable symbol of quality for all others.
Technical questions
Insulation
What products can be used under the footings when insulating under the concrete floor slab? Is this even necessary?
Ideally, a continuous thermal envelope should be created. Therefore, under the footings an insulation material should be used. There are several systems certified by PHI. Products/materials suitable for load bearing insulation include, for example, foam glass boards, foam glass granulate and XPS. However, the ideal solution (thermal bridge free) would be a foundation slab, without the need for strip foundations.
Ducting
Is it best to use rigid or flexible ducting within a heat recovery and ventilation system?
Rigid ducting is preferable and recommended as it is easier to clean if needed and does not result in the unfavorable pressure losses that flexible ducting produces. Rigid ducting, where possible, is therefore best.
Climate data
Where can I find suitable climate data for EnerPHit verification with the Passive House Planning Package (PHPP)?
If climate data for your locations are included in the PHPP, you should use these. For all other locations you can use the climate data tool on www.passipedia.org for orientational calculations (iPHA membership required). Before renovation work starts you should contact a Passive House Certifier in order to receive validated climate data for your location.
Where can I get reliable climate data not included in the Passive House Planning Package (PHPP)?
The PHPP requires two types of climate data: a set of monthly temperature and radiation data in order to be able to calculate the heating/cooling demand and a set of heating/cooling load data to be able to calculate the building's heating and/or cooling load. The data must be representative of the typical conditions over the entire year for the location at which the Passive House building will be built.
Monthly climate data is available for most locations as it is recorded at local weather stations or via satellites. There are different ways of accessing this information and converting it into the format required for the PHPP. One example is the climate database Meteonorm.
Generating heating and cooling load data is much more complex as they must take the dynamics of Passive Houses into account. The Passive House Institute can generate this more complex data for a cost of €400, plus 19% VAT per set. iPHA members receive a substantial discount.
Please contact iPHA if you require a climate data set that is not included in the PHPP and we will forward your request to the Passive House Institute.
What special considerations must be taken into account when using the PHPP in the Southern Hemisphere?
When using the PHPP in the Southern Hemisphere, all climate data must first be manually manipulated in order to deal with a few Northern Hemisphere biases in the PHPP.
The current PHPP assumes that the warmest period of the year falls from June to August.
>> Therefore, the data for the first half of the year, January through June (months 1 to 6), must be placed in the July through December fields (months 7 through 12) and vice versa for the data from the second half of the year.
The current PHPP assumes that solar radiation is coming from the south.
>> Therefore, the radiation data must also be entered backwards so that radiation coming from the north is placed in the field for southern radiation and vice versa.
>> Due to this change, the wall and window areas must also be adjusted so that areas facing north are entered as if they were facing south and vice versa. Note: this is relatively easy with areas facing either directly north or directly south, but becomes difficult when, for example, a wall is positioned 30° to the north – in this case, a 150° must be used for PHPP (to minimise errors, PHI suggests flipping the plans along the x-axis with the use of CAD or a similar program)
The Passive House Institute's Southern Hemisphere Climate Data Tool was developed to help you with the above.
Airtightness measurements
What must be included in the volume measurement for calculating airtightness to PH certification Standard? Must volumes in areas that are within the thermal envelope yet above or below an un-insulated and not necessarily airtight ceiling or floor be included?
According to page 8 of the Fachverband für Luftdichtheit im Bauwesen's (German Association for Airgtightness in Buildings) explanatory sheet on the EN 13829:2001, the entire volume from the uppermost layer of the flooring to the lowermost layer of the ceiling in the building’s final state should be used, even if, at the time of measurement, these ceilings and/or floors are not yet complete. Generally this means that if a volume above a hung ceiling or below a floor will not be visible in the building's final state, it should not be included in any measurement of airtightness.
Who is qualified to perform air pressure tests for Passive House buildings? Is there a third party certification system for such experts?
The person performing the air pressure test should have sufficient expertise and the measurement must be carried out in accordance with ISO 9972 (EN 13829 in Europe).
In Germany, certification of professionals is awarded by the Fachverband für Luftdichtheit im Bauwesen's (German Association for Airgtightness in Buildings). Similar associations exist in various countries worldwide. However, there is, as of today, no global certification system for airtightness experts.
Can I use OSB boards for my airtight layer? Are they always airtight?
OSB boards are often used as an airtight layer, generally with more or less acceptable results. The quality of different boards from different manufacturers differs greatly, however, meaning that some are more airtight than others (see this PHI study). It is always best to ask the manufacturer directly for a q50 value if concerned, especially for larger projects. Generally, q50 values of 0.1 (m3/(m2h)) or lower can be considered safe.
Doors and windows
What kind of door can be used to achieve an airtight connection from an unheated garage or cellar to a heated living area?
The best way is to use a Passive House suitable entry door. There are a variety of suitable Passive House Certified products visible on the Passive House Institute Component Database.
Non-residential buildings
Do non-residential buildings with special usages that require high energy loads have to met the 120kWh/(m²yr) criterion?
The criteria for non residential buildings come with a special note on the first page that makes an allowance of sorts for such cases. Indeed, in certain cases, where the building's usage implies high internal heat loads, the primary energy limits may be exceeded after consultation with the Passive House Institute. For buildings with special uses such as hospitals and wellness spas, the Passive House Institute is currently in the process of defining sensible criteria. Beware though, as this is NOT a free pass to ignore the primary energy demand: should you wish to get such a building certified, the certifier on the project must discuss your exceeding of the limits directly with Passive House Institute and it must be proven that electric energy was used as efficiently as possible.
Heating in a Passive House
What do I need to look for in a Passive House suitable pellet stove?
The stove has to be airtight and the supplier needs to confirm that the stove is suitable for Passive Houses. For safety reasons, we recommend a CO2 sensor and control to be installed in addition so that, should high CO2 concentrations arise, the stove or the ventilation unit is then automatically switched off. A detailed explanation can be found in the course material used by many Certified Passive House Designer examination hosts for their Certified Passive House Designer Training, as well as in Passive House Institute's Protocol Volume 36. We suggest working with a Certified Passive House Designer for assistance. While the Passive House Institute certifies Passive House components, a stove is not mandatory in a Passive House and Passive House Institute has thus not certified Passive House suitable stoves.
Go back to FAQ index
What are the advantages and disadvantages of underfloor heating in a Passive House?
Usually, underfloor heating is implemented because people desire the comfort of warm feet. In the Passive House however, this is achieved in any case due to the excellent insulation. User experiences confirm this:
An underfloor heating system will have relatively little effect in the Passive House in terms of increased comfort. Due to the smaller heating power, it is unlikely that the floor temperature will get much warmer than 24°C. However, if at all, this temperature will only occur as a maximum winter temperature, i.e. in the heating load case. In order to achieve warm feet, it would be more expedient to select the correct type of floor covering and to give preference to “warm” materials like wood (lower heat dissipation).
An advantage of underfloor heating is that it requires very low flow temperatures, therefore in the Passive House, such heated surfaces can be successfully coupled with systems that provide low flow temperatures (e.g. heat pumps). A disadvantage is that such a system is not a cost-effective supply variant for a Passive House. In the Passive House, it does not matter how and where the small amount of residual heat is supplied. For achieving this cost-effectively, it is possible to use the ventilation system, which is essential in any case, for heating as well. Nevertheless, various Passive Houses with underfloor heating systems have been realised.
Ventilation
How can I balance ventilation ducts?
Especially if you want to balance the fans with the help of individually measured values, you'll need a precise measurement of air flow rates. We recommend the use of a device called a flow finder, which tends to be far more accurate than an anemometer, as it is equipped with an auxiliary fan that compensates the additional pressure difference of the hood.
Is the ventilation system noisy?
A ventilation system, that is designed and executed with care will not be audible in standard operation mode. Most ventilation units should be installed in a utility room or another area not too close to the bedroom. Ducting systems needs to be fitted with silencers. The home will also be better protected against noise from outside.
Is it necessary to install a mechanical ventilation system with heat recovery (MVHR)/HRV, or may I use windows for ventilation?
Using windows for ventilation can help reduce pollutants in the indoor air but it is not suitable for energy efficient building renovation. Buildings with very low energy consumption and very high airtightness levels have a mechanical ventilation system combined with heat recovery (MVHR/HRV). This system ensures a healthy indoor microclimate and as a benefit, you save more than 10 times the heating energy, compared to the electric energy for running the ventilation system.
Does a ventilation system need maintenance?
Yes. Air filters need to be replaced once or twice a year. The ductwork is normally protected from dust by the filter and doesn't need to be cleaned. If your ventilation system doesn't have automatic flow balancing, the airflow volumes should be recalibrated after several years.
What are suitable ventilation concepts for renovation?
Depending on the floorplan, centralised systems with a heat recovery unit for several apartments or decentralised systems with one unit for each apartment can be used. Cascading ventilation concepts are recommended, if the floor plan is suitable because they need less ducting and are more efficient. Ventilation units integrated into windows still do not have the necessary efficiency but products are in development. Ventilation systems always need to fulfill two criteria: 75% heat recovery efficiency as defined by the PHI and a max. electrical consumption of 0,45Wh/m³ of ventilated air.
What is cascading ventilation?
In a cascading ventilation concept, some of the living areas are treated as overflow zones. This means that there is less ductwork required and the amount of ventilated air is minimized.
In which refurbishment step should a Mechanical Heat Recovery Ventilation (MHRV/HRV) be installed?
Once the airtightness level is upgraded (at least 1 air changes per hour at 50 Pa), which should be achieved upon the upgrade of walls, roofs, floors, windows and doors, a MHRV/HRV must be installed. If a MHRV/HRV is not installed as soon as the airtightness level is achieved, the risk of extremely poor air quality within the building is very high and it will not be safe to live/work in it. Moreover, without a MHRV/HRV the moisture content within the building will rise considerably putting the building fabric at risk.
The exhaust air outlet and fresh air inlet are often situated close to each other in Passive Houses and EnerPHit retrofits. Does this cause problems with mixing fresh and exhaust air?
In many countries, there are strict regulations for the separation of the exhaust air outlet from the fresh air inlet. Experience from Passive Houses shows, that giving different directions of the airflow through the exhaust air outlet and the fresh air inlet is sufficient to ensure good air quality.
I love cooking. Will the heat recovery ventilation be able to vent off all smells and vapor?
The air inlet in the kitchen should have a grease filter. If you cook large meals frequently, an additional kitchen hood with a carbon filter is recommended. It should preferably recirculate the air instead of venting it off to the outside, as this causes high heat losses.
Are radon gas and its decomposition/decay products in well-insulated buildings dangerous?
Radon is a noble gas which occurs in the decay chains of uranium and thorium; radon itself is subject to radioactive decay. It is *-active (alpha decay due to emission of a fast helium nucleus) with a half-life of 4 days and its decomposition products in turn are radioactive themselves. The main source of radon in buildings is the ground under the buildings, and it is released by mineral building materials (natural stone, concrete, plaster, clay, bricks etc.). If higher concentrations of radon are present, then the main source in most cases is the ground rather than building materials. The reason for this is the uranium content of the ground and rocks. Radon pollution levels fluctuate greatly depending on the location of the building (uranium content of ground), type and quantity of the building materials as well as airtightness of the closure against the ground and the air change rate. (Natural) radiation exposure due to radon and its decay products is, in fact, a serious risk. The current mean concentration for radon in indoor air is approximately 50 Bq/m³, the mean equivalent dose is about 15 mSv (1500 mrem) in the bronchial epithelium and about 2 mSv (200 mrem) in the alveolar regions of the lungs. Of the approximately 50,000 lung cancer deaths each year in Germany, a relative percentage of 4 - 12 % (about the same for men and women, smokers and non-smokers due to synergistic effects) is attributable to the inhalation of radon and its decay products: that is about 2,000 to 6,000 cases per year or 0.1 to 0.4 % of all deaths. This demonstrates that the issues with radon gas need to be taken seriously.
The most effective measures for reducing radon pollution in homes are as follows:
· Sealing against the entry of radon from the ground
· Removal of radon from the ground by means of active or passive ventilation of the basement
· Possibly sealing of walls against indoor spaces (vapour barrier) that are made of materials with a particularly high uranium content (basalt, other heavy building materials – must be measured!)
· Ensuring adequate fresh air supply e.g. through active ventilation, or even better, through heat recovery from extract air.
None of the measures mentioned above stand in contrast to high energy savings in the residential sector. Appropriate thermal protection measures do not lead to any increase in radon pollution; on the contrary, they can be combined with measures for the reduction of radon levels:
· Lightweight building materials that have no or very little (organic) uranium content are suitable insulation materials
· Thermal insulation on the outside of exterior walls, or the insulation of roofs and attic floors does not affect radon concentrations in indoor spaces. The same applies for window panes with good U-values (particularly low-e glazing). But: see the comments relating to airtightness and windows!
· Airtightly executed insulation of the basement ceiling can be combined with effective sealing against radon emissions from the ground. In this way, radon pollution will be effectively reduced.
· When implementing interior insulation, the application of a vapour barrier on the inside is recommended. This simultaneously constitutes an effective barrier against radon released by building materials of the walls.
Insulation measures (reduction of thermal conductivity through building components, referred to as transmission heat losses) should not be confused with airtightness sealing measures (reduction of ventilation heat losses). As shown above, thermal insulation is neutral or even mitigating in relation to radon pollution. The highest energy savings in housing stock are also achievable through insulation and not through airtightness. The following applies with regard to the reduction also of ventilation heat losses:
An adequate air change rate is imperative in inhabited spaces for a whole range of reasons: the removal of odours, CO2, harmful substances from furnishings etc., also the removal of water vapour (to avoid structural damage – mould!) for achieving a low equilibrium level of radon.
If, as is the case in modern buildings, the exterior envelopes of the building are executed in a meticulously airtight manner, then adequate ventilation must always be ensured. Ventilation through windows by occupants is a possible solution, but it is not the best solution. The PHI always recommends the use of a home ventilation system. Good results have been obtained with extract air systems in existing and low energy buildings.
A solution that greatly reduces radon concentrations and saves energy is the use of a home ventilation system with heat recovery. Here too, the solution that most effectively reduces radon pollution is the optimal solution in terms of energy efficiency.
Measurements in Passive House buildings with excellent home ventilation systems showed radon concentrations which are significantly below average comparative values
Centralised vacuum cleaning system
Is a centralised vacuum cleaning system compatible with a Passive House?
A centralised vacuum cleaning system is possible in a Passive House if desired. The ventilation system does not even have to be turned off during operation of the system, as:
- the air quantities for vacuum cleaning are not as great as for an extractor hood, for example.
- the duration of use is short as vacuum cleaning does not take two hours (whereas extractor hoods can be operated two hours long when necessary). Any openings towards the outside should have baffles and be airtight and insulated.
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EnerPHit retrofitting
Is it cheaper to retrofit step by step than in one shot?
With a step by step retrofit, the investment is spread over several years. In doing so, each component can be retrofitted when it has reached the end of its service life, maximizing the utility of the investment in energy efficiency.
As less money is required to complete an individual step rather than a complete retrofit, work can be started sooner to realize savings on energy bills sooner. The financial gains can be greater than the additional costs specific to the step by step retrofit process (e.g. setting up scaffolding several times).
Are there special products available for step by step renovation?
There is a manifold of Passive House components available on the market. Most can also be effectively used for retrofits. Some products can be used in an adapted form or as part of an optimised concept for renovations. Some special products are in development and we expect the number of available products to increase in the future.
How can renewable energy sources (RES) be integrated into a renovation project?
When changing the roof or the facade, the integration of Photovoltaics (PV) can be meaningful, if it does not have a negative impact on the architectural quality of the building. It makes sense to use the produced energy on site in combination with heat pumps and to feed any surplus into the general grid, if possible.
What is the most cost-effective first retrofit step?
It differs from building to building. This can be accurately analysed with the Passive House design tool - Passive House Planning Package (PHPP). In principle, an overall step by step retrofit plan should be designed outlining the costs and savings of each step. The savings that one can achieve from each step can be calculated and then allocated in the next retrofit step.
What should be prioritised in a step by step retrofit - the renewables or the building fabric?
Definitely the building fabric. By improving the energy performance of the thermal envelope you are reducing the primary energy demand of your building considerably. The small remaining demand can then be covered by renewable energy much easier.
Is the EnerPHit standard suitable for my building?
In energy retrofits it is often difficult to meet the Passive House criteria, even if you use the same components (for the walls, roofs, windows, etc.) as with new buildings. Some parts of the buildings are not accessible, so some thermal bridges would remain. This is why the EnerPHit standard has been created for renovations close to the Passive House concept.
Can we have a fireplace in an EnerPHit building?
A Passive House is very cosy without a fireplace, but technically, yes it is possible. Instead of an open fireplace, an airtight wood stove which receives the combustion air from the outside needs to be used. The stove should be as small as possible as the heating power tends to be much too high in very efficient houses.
Can we open the windows in an EnerPHit building?
Windows can be opened whenever you like. Window opening is not necessary, however, because the heat recovery ventilation system constantly provides sufficient amounts of fresh air without any uncomfortable draught. In summer, the ventilation system can be turned off, if desired, and windows can be opened for ventilation.
Is there any requirement that has to be fulfilled in the intermediate steps of a step-by-step refurbishment?
The approximate insulation level or efficiency level of the intermediate steps should be defined in the Overall Retrofit Plan (ORP) before the implementation of the first step. The certifier will make sure that the ORP complies with the requirements for EnerPHit renovation. If one adheres to the levels defined in the ORP for each step, you will achieve the EnerPHit standard for the building as a whole in the end.
What are the wider societal benefits to undertaking energy efficient refurbishment?
The refurbishment of the building stock provides an opportunity to create local jobs, stimulate the economy and at the same time generate savings. For example, in Germany, the KfW handles the promotional programs on behalf of the Federal Government. The programs for energy-efficient construction and refurbishment receive favorable terms through German federal budget funds to provide financial incentives for higher energy efficiency levels in the housing sector. Recent studies show that in Germany, energy efficiency refurbishments of buildings is a win-win situation for the homeowners, the environment, the economy and the federal budget, according to a study by Forschungszentrum Jülich.
Can I reach the EnerPHit Standard in a large building when I cannot put insulation on the ground floor, for example, because the residents must stay in the flats whilst the work is carried out?
It may be possible to achieve the EnerPHit Standard without any basement ceiling insulation. This problem can be addressed by installing a perimeter skirt of insulation to trap the heat below the slab. You can calculate the effect of the perimeter skirt with the PHPP Ground worksheet, but additional dynamic simulation would be recommended for further optimisation.
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Can the EnerPHit Standard be achieved in a large building with direct electric domestic hot water units?
EnerPHit primary energy requirements can also be achieved with direct electric heat generation if other parameters are optimised. It is, however, not recommended.
Which basic principles should I adhere to if my first retrofit step is to upgrade all windows and doors?
In principal an overall step by step retrofit plan should be in place from the beginning, thus the upgrade of the thermal envelope is defined in particular the type, thickness and location of a new insulation layer. The window/door jamb, head and sill details must be designed to minimise or avoid any thermal bridging/air leakage/condensation risk. If the windows and doors are being installed prior to the upgrade of the walls, these should be located along the future wall insulation layer, safeguarding the integrity of the new windows/doors and the existing walls. There will be two types of window/door installation detail sets: one for the first retrofit step of upgrading windows/doors installation on the existing wall, and another for the upgraded windows/doors installation on the upgraded wall.
Is the Passive H+C17ouse retrofit standard EnerPHit always the best economic choice for step by step refurbishment?
A retrofit to an energy efficiency standard lower than EnerPHit may save on initial investment costs, however in the long term, more money will be spent on energy bills and the building will not hold as high of value. The less efficient an existing building is, the higher life-cycle costs will be. The EnerPhit standard seeks for an optimal investment in different climates and different architectural contexts.
How can we effectively follow a refurbishment that will last 10 or 20 years? Who will take care of that?
The EuroPHit project will produce exemplary refurbishment plans that anticipate the overall workflow for the step by step retrofit. Using these plans, along with the construction details for each step, future design and construction teams will have a thorough understanding of what has already been done and what remains to be completed.
How can step-by-step refurbishments be financed?
Step-by-step refurbishment constitutes the most appropriate approach, in most cases, for energy efficient refurbishment, both from the building perspective (modernisation where and when needed) and from the point of view of the house owners with limited financial resources. Building retrofits generate energy savings over the lifecycle of the investments, therefore long term financing is needed. Getting finance right is the first step in the provision of the complete solution.
The financing of step-by-step refurbishments is a key element of the EuroPHit project. Significant levels of research and industry interaction is informing the development of financial guidelines which will provide an economically viable and attractive solution. The intention is that financial institutions will offer financing for step-by-step refurbishment projects that meet certain criteria.
What are the market barriers to financing refurbishment?
The EU has identified the following barriers to the use of financial investments for sustainable energies (SE) in buildings including energy savings and renewable energies:
• High pre-investment development and transaction costs partially due to small size of projects, especially in the residential sector;
• Information failure on the part of customers: lack of customer awareness and a very high perceived risk of new more efficient technologies by both users and financiers, mistrust in energy audits, benefits initially invisible;
• Information failure on the side of commercial financial institutions (CFIs): general lack of sustainable energy (SE) finance experience within commercial financial institutions, lack of dedicated time and resources to develop SE capacity and activities in-house;
• Lack of visibility and scale of SE finance: SE projects often represent a relatively small niche business for major banks;
• High perceived end-user credit risks;
• Low collateral asset value of SE equipment and difficulties creating creditworthy financing structures. Collateral value is low because for most SE projects equipment represents a sizeable share of total project cost with high portions of engineering, development and installation costs;
• Energy savings as revenue is foregone by financiers: cash flows from saving energy are not (yet) conventional revenues in what is still an asset-based culture in financing. This discourages commercial financial institutions entry into this market. Energy cost savings should be incorporated into lenders' analysis of free cash flow and ability of borrowers and end-users to meet debt service payments ;
• Even where payback periods are short and economic benefits clear, SE projects are often not implemented because of high upfront costs;
• In the rental sector: Spilt incentives between building owners and tenants;
• In the residential sector: long payback periods, lack of contractors, small project size and lack of support for holistic retrofits.
What are the legal barriers to financing refurbishment?
The EU has identified the following legal barriers to the use of financial investments for sustainable energies (SE) in buildings including energy savings and renewable energies:
• Public sector: the rules of public budgeting – including the annual budget cycle and multiannual savings cash flow – make it difficult for public entities to finance energy efficiency investments from savings in energy costs (similar rules exist in large companies);
• Public sector: local authorities may have to finance energy efficiency investments from their investment budget whereas the resulting savings are credited to the operational budget;
• Residential, joint homeownership: Ambiguities in the legal standing of joint home ownerships and lengthy and cumbersome decision-making due to a large number of decision makers (residential sector); In the case of properties which are managed by housing management companies, steps for renovation are only undertaken with great reluctance, especially if the proportion of rented units is very high. Here, better living comfort and yield (profitability from rental) are not always aligned. Statutory regulation of renovation cycles normally do not include energy efficiency investments
• Residential and rental sectors: uncertainties related to tenant-owner issues and building ownership;
• All sectors: not considering life-cycle costs in procurement decisions.
What are the barriers to undertaking refurbishment in residential buildings of joint homeownership?
Specific issues arise with blocks of flats with individual owners, whereby owners' associations need to be involved in line with the specific legislation and practices. It should be noted that achieving energy savings in multi-apartment buildings with common heating/cooling systems often depend not only on the overall energy efficient retrofit of such buildings but also the behaviour of end-users. It is also important to ensure that such renovations pay due attention to the ventilation systems, maintaining a healthy indoor environment. The cost for individual energy metering in multi-apartment housing renovated to EnerPHit standard can form a significant fraction of the total running costs, as energy costs are so low. In some pilot projects individual metering of heating and hot water has been omitted for this reason.
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How can the owner-tenant dilemma be overcome?
The following are some suggested ways to overcome the owner-tenant dilemma for refurbishment projects:
• Collect relevant information to understand the context of the community.
• Analyse the needs of the residents by observing routines and behaviours.
• Make tenants an integral part of the retrofit process, by understanding their needs and responding to them appropriately.
• Provide ‘show projects’ to demonstrate how the completed project will look and feel.
• Establish confidence between the different parties by being approachable and trustworthy.
• Continued communication and interaction with different stakeholders, using a range of different methods.
• Ensure that the construction works are undertaken in a sympathetic way, causing minimal disruption to residents and the local community.
• The owner should not increase the rent more than the expected heating costs savings, This way both sides will benefit from a financial profit.
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What are the existing financing models for refurbishment in the EU?
Funding sources and promotional programs offered in Europe are listed on the following webpages of the EU, see http://www.buildup.eu/financing-schemes. Schemes are catalogued as follows:
• Europe-wide funds
• National/regional schemes for individuals
• National/regional schemes for municipalities, social housing
• National/Regional schemes for residential Buildings
• National/Regional schemes for non-residential Buildings
What is a one-stop-shop for refurbishment?
One of the major barriers perceived in scaling up the amount of retrofits taking place is the fragmentation of the retrofit process between measures/organisations and how clients can access the information they require. One-stop shops, where multi-disciplinary teams can undertake all elements of a refurbishment project, are considered to be a way of alleviating a number of issues in the retrofit market.
One-stop-shop models are where multi-disciplinary teams can undertake all elements of a refurbishment project, including surveying, design, construction, and financing. This may involve one or more organisations, working in a joined-up way, to provide an end-to-end offering for a client. Potential business models for one-stop-shops are being explored as part of the EuroPHit project.
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What is the value of quality assurance in refurbishment projects?
The issue of quality assurance is extremely important, especially when aiming for a demanding performance standard such as EnerPHit. Quality assurance procedures ensure a consistently high level of value for money for all. Improper quality assurance could jeopardise the certification of projects and lead to potentially expensive remediation measures. Through research and industry engagement, the value of quality assurance in refurbishments is being thoroughly considered as part of the EuroPHit project.
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What are redemption grants and how are the used?
In case of a step-by-step retrofit (as in the case of the EuroPHit project which implements the EnerPHit standard) a repayment bonus financed from a grant (redemption grant) can be used in connection with loans to reward the borrower when certain efficiency targets of the EnerPHit standard have been achieved.
The KfW, Germany, used redemption grants in their promotional programs for the energy retrofits of residential buildings. The redemption grants are refinanced out of the government budget. As soon as the retrofit achieved a certain level of energy efficiency comparable to the requirements of the energy saving ordinance for new buildings a repayment bonus was rewarded. The efficiency targets are defined as the calculated total primary energy demand of the whole building in kWh/m²/year.
