FAQ
Here you will find a selection of frequently asked questions with regard to Passive Houses.
GENERAL QUESTIONS
Passive Houses
iPHA
Education
The PHPP
Building and component certification
TECHNICAL QUESTIONS
Airtightness measurements
Climate data
Ducting
Insulation
Non-Residential Buildings
Heating in a Passive House
Centralised vacuum cleaning system
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):
>> Specific space heating demand ≤ 15 kWh/(m²yr) OR Heating load ≤ 10 W/m²
>> Specific space cooling demand ≤ 15 kWh/(m²yr)
>> Annual overheating hours (indoor temperature over 25°C) ≤ 10%
>> Airtightness test result n50 ≤ 0.6 air changes/h
>> Total specific primary energy demand ≤ 120 kWh/(m²yr)*
The aforementioned criteria are functional and based on the ability to heat the house soley 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.
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 Passive House criteria. For more information on Passive House certified building 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 convential 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 consistantly and predictably low: the expected consumption agrees well with average actual consumption, even given a great variety of occupant habits and lifestyles.
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 employee 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 about 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.
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 Support 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 air speed 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 normal 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 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 and the iPHA forum.
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. Click here for a list of typical professions. Consultants, on the other hand, can come from any background.
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 list of PHI accredited examination bodies
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.
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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 usign 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 over night, 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 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 recieve 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
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 Intitute 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 it's 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.
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How can Passive House be both a “public good” and at the same time a matter of contractual certification?
Passive House IS a public good. 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 a public good 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 of 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 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 fliping the plans along the x axis with the use of CAD or a similar program)
The Passive House Institute's Southern Hemipshere 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.
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.
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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.
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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