A Passivhaus (Passive House) renovation?

The picture on the left is a thermograph – showing the difference in lost heat between a conventional house (on the left) and a house built to PassivHaus standards (on the right). Which house would you rather be living in when Russia cuts gas supplies? 

The PassivHaus standard, as interpreted for the UK by the AECB, should result in an 80% reduction in a house’s energy consumption. PassivHaus design concentrates on three areas: improving the air-tightness of the house, reducing heat bridges, and, to a lesser extent, considering heat gain from the sun.

In essence, a typical passivhaus is air-tight & super-insulated, with mechanical ventilation with heat recovery (referred to as MVHR) to solve the issue of internal air quality. I had always believed that a PassivHaus needed no extra heating, but apparently that’s not entirely true. While they’ll generally have no radiators or underfloor heating, they often do have a small heating element within the ventilation system. In general they require about 30cm of insulation, and windows that are triple glazed.

Here are some of the key points of interest to me from the AECB version of the standard:

• Use daylight to displace use of electric light
• Solar hot water system required to deliver at least 50% of hot water
• Walls, Floors, and Roof to all have U values of <= 0.15W/m2K
• Doors (uninstalled) should have a U value of <= 0.6 W/m2K
• Windows (uninstalled) should have a U value of <= 0.8 W/m2K, with a solar energy transmittance (inc frames) of >= 35% and a visible light transmittance (inc frames) >= 50%
• Rooflights (uninstalled) should have a U value of <= 1.0 W/m2K
• All habitable areas to have a glazing area (excl frames) >= 14% floor area
• Typically space is heated with hot water coils within the MVHR ducts
• MVHR should recover at least 75% of heat, with a fan using <=1.44W per l/s
• Any non-solar water heating to be Gas Condensing boiler or CHP – wood fired stoves are not permitted (this conflicts with my peak-oil resilience planning)
• Insulation on water tanks to be at least 100mm PU foam, all pipes and valves to be insulated with at least 40mm mineral fibre, and all cold pipes to have a vapour barrier
• Lighting to be >= 50lm/W
• Use the most efficient appliances – A/A+ minimum. TV to be LCD.
• Use a heavy-duty membrane to air-proof the house.

In conclusion, this is a great list of targets which I may I don’t think I’d go for PassivHaus certification, even though I like the overall aims – my Peak-Oil resilience planning needs things that are proscribed by the standard – like a wood-fired stove!

 PassivHaus Resources

• Wikipedia on Passive Houses – good basic intro to passive house design
• Villavent – Suppliers of Heat-Recovery ventilation systems, with a good description of how and why.
• PassivHaus Institute – the institute for maintaining Passivhaus standards
• The Independant – article on the basics
• Green Building Forum – discussion on a passivhaus renovation
• Association for Environment Conscious Building (AECB) – documents detailing their UK interpretation of the passivhaus standard and their higher, Gold standard. A good PDF to start with is this one
• AECB Forum – refurbishing to PassivHaus standards
• HouseBuilder’s Update – review of a UK PassivHaus, and maintenance of MVHR systems
• Passive-On – download a demo copy of the PassivHaus Planning Package software
• House of the Future – an Austrian PassivHaus renovation project – full of details on how to renovate to PassivHaus standards
• Simmonds Mills – UK architect builders, doing a passivhaus renovation in Hereford
• Passive House Retrofit Kit – essential guide to how to convert every part of your current house to Passivhaus standards
• GreenSpec – PassivHaus in the UK
• Green Building Press – discussion on the nuber of solar panels required to power a PassivHaus
• PassivHaus UK –  the BRE’s guide to PassivHaus in the UK, including suppliers of ventilation systems and airtightness solutions
• Passive House Solutions – suppliers of vacuum insulated panels – up to 10x the value of standard insulation
• Drexel und Weiss – Make an ingenious ventilation module with heat recovery, a mini heat pump for air and domestic water heating and a domestic water storage tank.