Have received a lot of questions via the website, house visitors and looking at the search words for this blog, so have decided to answer the first tranche via an FAQ:
How many passive houses are there in Ireland?
I reckon at the moment there are about 10 certified in this country but many more in the pipeline.
Search function on PHI website: http://www.passivhausprojekte.de/projekte.php?lang=en
UK Passive House Map: http://www.passivhaustrust.org.uk/projects/
What is the PassivHaus Institut?
The Passivhaus Institut (PHI)was founded in 1996, by Dr. Wolfgang Feist, as an independent research institution. It employs physicists, mathematicians and civil, mechanical and environmental engineers, performing research and development on highly efficient energy use. Based in Darmsdadt in Germany, they are the though leaders in the field of lowe energy building design. The PHI certify the design and construction of ' Certified' passive houses and sets the exams for professionals training in the area. The use of the term ' passive house' or 'passivhaus' is not trademarked so so whilst the term is often used casually, just like the term 'Hoover' or 'Tupperware', it is only buildings that have official certification that have genuinely & officially reached the quality standard demanded by the PassivHaus Institut
Wed address: http://www.passiv.de/
What is a passive house certificate & how does it differ from a conventional build
In Ireland, & maybe in other jurisdictions, the design of any house is undertaken by an architect with regards layout, planing permission, massing etc & the structural design undertaken by a structural engineer. These professionals with then come up with design details that the contractor should use. The construction process is then 'monitored' ( whatever that means) – perhaps via 4 or 5 site visits - by an engineer / architect and 'self certified' ( hard to believe...but true) as meeting the quality standard required by the building regulations and Technical Guidance Documents. There is little inspection of builds by building control or local enforcement function.
The process of certifying a house is an additional leg to the process whereby the energy demands of the building are modelled, via an excel tool call the PHPP ( Passive House Planing Package) to meet strict requirements. Then to confirm that the build meets the requirements, photos, details of material, junction details and airtightness test results are detailed. These are send to the PHI in Germany or the local approved certified for certification as meeting PHI Passivhaus design and construction requirements.
The Passive House Enyclopedia : http://passipedia.passiv.de/passipedia_en/start
Self building a passive house a good idea?
Not sure I can answer this question in anything less than 5000 words! In short, any self build should not be undertaken lightly; a self build of a passive house requires a whole different level of attention to detail in design and construction – much of which is new to the vast majority of site personnel & tradesmen. As mentioned earlier in the blog , in a tight market everyone is selling something & it pays to be a sceptical & informed client. Bottom line is that savings of going self build may cover the additional costs of a passive house over a more standard build.
Disadvantages of a passivehouse
The single biggest challenge is the additional capital cost of the build.The second biggest one – according to my wife – that there is no open fire!
Does a passive house have a heating system
Yes, unless there are sufficient solar gain, heat losses from other sources ,enough people and activities to make the building a 'comfortable' temperature. The key term here is ' comfortable'; there are people who think 21C is toasty & necessary; other say that anything above 17C is far too warm & stuffy. In addition, bedrooms should typically run a few degrees cooler. In summary, one man ( or woman's) hothouse is another man's ice house.
What sort of heating system does a passivehouse have?
There is no one answer to this & very much depends on your location & requirement. The key thing is that it should be a small & efficient unit, given that the building will overheat very quickly Options out there include
- Preheating the air on the way using a water to air radiator
- Sealed fires
- Radiators
- Radiant panels
- UFH - water or electric
What materials are used for air tightness?
These depends on the surface
- Floor :A screed cement / concrete layer is accepted as airtight
- Walls : 18mm Orientated Strand Board ( OSB) – it looks like a plywood – as the internal sheathing board is generally accepted as being airight in the long term. The joints between the boards are sealed using airtight tapes e.g. Siga tapes. Thinner boards are much less airtight but are cheaper & easier to work with.
- Roofs : working at height with OSB is very difficult due to their weight. The more common approach is to use various proprietary membranes. These membranes are also used at some of the junction details to ensure air tightness
Windows in a passive house
In general where possible, at a design stage the room layouts is optimised so that rooms that need natural light , e.g. Living rooms, kitchens, are south facing ( to capture the benefit of solar gain) and those that don't e.g. Utility rooms, bathrooms are north facing. There are many windows are certified by the PHI as meeting their specific energy loss requirements ( this usually refers to the frame which is generally manufacturer specific). Other important components though include the glazing panels, spacer that separates the glazing & the fill gas. The frames are made from the usual materials : woods & PVC. There are a number of questions about the longevity of PVC frames given that the triple glazed panels are extremely heavy and I would look for a manufacturer to have a long track record in case the PVC sagged over time. Passive certified windows are significantly more expensive & bigger than standard windows we are all used. That being said, they are exceptionally solid & sound proof .
Foundations ina passive house
There are a large number of proprietary insulated foundation & slab designs on the market but as previously mentioned they are extremely expensive. It is definitely possible to achieve the same levels of insulation and thermal bridging using readily available materials such as EPS. There is a book of accepted Passive House design details available on Amazon which will suggest some options. As a measure many modern houses have floor U values of about 0.16 W/m2K; for a passive house you are looking for about 0.1W/m2K
Why did you use panelvent on the roof?
As a sarking board to reduce the impact of wind on the roof level insulation as we used a warm roof construction. Panelvent is a 9mm wood fibre board which is rigid but moisture permeable.
Running services in a passive house
Really no different to any services layout – keep it simple when possible & keep the runs short. Any good design should stack bathrooms on top of each other to minimise runs. Levels of insulation of all services very high by comparison to usual Irish workmanship standards.
If you have a question that I can help resolve , would be happy to answer & post in the FAQ section.
