So, what is Passive House? Essentially, it’s a building in which you can maintain a pleasant temperature in winter as well as in the summer without a separate heating or air conditioning system. In laymen terms, that’s an annual heating bill of £80 – £120 based on current gas prices – less than one tenth of the price most householders currently pay.
A Passive House is not passive unless certified by the PassivHaus Institut or an authorised UK company.
What are the door design principles to consider for passive house design?
1. Avoid heat losses
As airtightness is such an important factor that at the end of a build, and/or when the building envelope is finished, this is verified through a blower door test. For a passive house the maximum acceptable leakage corresponds to an hourly air change of 0.6, i.e. a maximum of 60% of the volume of the air in the building is allowed to leak out/in in one hour at a pressure difference between the outside and the inside of 50 Pascal.
It is surprising just how much ventilation can pass through the gaps around a door. A standard door can pass 70 litres/sec at a pressure differential of 15 Pa.
2. Unbroken super insulation
- Virtually thermal bridge free construction
- High quality triple glazed windows - These address the first path via which heat is lost from buildings: conduction of heat through the building fabric.
- Very airtight building envelope -This addresses the second path via which heat is lost from buildings: infiltration and exfiltration of air though gaps in the building envelope, otherwise known as draughts.
- Mechanical Ventilation with Heat Recovery -Which addresses the third way heat is lost from buildings: via the deliberate introduction of fresh air and extraction of stale air for the purpose of ventilation.
So what are the restrictions on design that can happen?
Just like Secure by Design testing, if a door has been tested to a Passive house certification then every component needs to remain the same in order to meet that certification. So, that means that a door would need to have every component the same as was tested and it can’t be changed. This also relates to size. If a door is tested to a maximum size then you can’t change the size and still have the certification. This is only an issue if the house itself is being certified as Passive House.
Some clients build a house as Passive but don’t actually pay the extra needed to actually certify it. This is the same for doors. A door can be made to a Passive standard but not certified and that means you have more choice and design leeway.
What are the benefits of a door made to meet Passive House regulations?
Doors made to this certification can achieve a U Value of 0.89 and higher – a standard doorset would require a U Value of 1.2. This is achieved by the use of a thicker doorset usually at 98mm thick, with specialist hinges, threshold and weather sealing that ensure possible heat loss reduction. But it is essential to be aware that heat loss from fixing the frame to the building envelope is also just as essential.
Urban Front offer hardwood doors up to 1.1m x 2.2m in every design we do except those with glass vision panels.
For more information about Passive House, please go to: http://www.passivehouse.com
Go to https://www.urbanfront.com/en_GB/technical/door-specifications/front-e98-passiv/ for more information about our passive house doors.