Passivhaus (Passive House)
is one of the world’s fastest growing environmental standards for new buildings. As experienced PassivHaus Consultants, let us help you get there.
5 Key Stages of quality and value offering:
Understanding PassivHaus Commonly Asked Questions
Why would you choose Passivhaus?
Do you want £100 per year energy bills and be able to close windows to reduce noise but still be able to breathe? Sit in a tee shirt with an internal temperature at 20 degrees? Reduce hay fever and other allergies through a filtered mechanical ventilation system? Then this could be for you.
It really helps pass your planning permission to provide how energy efficient it performs and in real life, the actual house is very close to the predicted design stage outcome.
Using a Certified Passivhaus Consultant with experience in delivering this standard will streamline the process and help achieve Passivhaus Certification.
What is the Passivhaus Standard?
Passivhaus buildings provide a high level of thermal comfort using very low energy. The scheme was developed by Dr Wolfgang Feist using physics to accurately model and predict thermal comfort levels and energy demand for new buildings.
The Passivhaus Standard has several criteria to meet the Passivhaus Standard:
|External Fabric Average U Value||<=0.15 W/m2.K|
|Space Heating Demand||<= 15 kWh/m2/year|
|Space Heating Load||<= 10 W/m2|
|Air Tightness||<= 0.6 ACH|
|Summertime Overheating||<10% over 25 degrees C|
The standard seeks to balance thermal efficiency (reducing heat loss through the walls, floor, roof, windows, doors and thermal bridging) with minimising external openings that could cause summertime overheating.
The Mechanical Ventilation with heat recovery means you are capturing up to 93% of the heat from the extracted air, significantly reducing the need for space heating.
Air tightness reduces uncontrolled draughts which cause discomfort. The ventilation system (if installed correctly) while silently provide all of the air you need, 24 hours a day.
The heating system is minimal. A typical 100m2 house could have 2 x 0.5kW electric panel heaters to heat the whole house.
If you are warm, day or night, you can open windows, boost the ventilation system and balance airflow to keep you cool and comfortable.
How do you achieve the Passivhaus Standard?
We strongly recommend this starts at design inception. Getting the orientation right and the form factor (external heat loss area divided by the floor area) at the start is really helpful to stand a good chance of passing while minimising expenditure.
Keep the form simple and think about ensuring insulation continuously wraps the structure to minimise heat loss through thermal bridging.
Keep windows and door simple. Reduce mullions and transoms so window openings provide more glass so the can reduce in size to allow adequate sollr gains balanced with minimising summertime overheating.
Think about junctions and ensure heat loss is controlled by instructing thermal breaks. Even location of windows in the external walls really help reduce heat loss.
Air tightness is key and having the right strategy that is practical to apply from the start and carry out regular air tightness tests after each relevant stage to check you are on target.
And use a really good Mechanical Ventilation with heat recovery system (MVHR). We recommend Paul or Zehnder and their Passivhaus certified systems, preferably with summer bypass. We have used Green Building Store for design, supply and commission and the system has been excellent with near silent running.
How can Low Carbon Box help?
We have been the Certified Passivhaus Consultants on 19 dwellings across 3 sites and also carried out air tightness testing so have an integral knowledge of the details and results. The Passivhaus standard is highly challenging but knowing the pitfalls from experience really helps on the next project.
If Passivhaus is daunting, then why not try the AECB Building Standard. This uses many of the same principles with more flexibility.
Our Certified Passivhaus Consultant also has an MSc in Energy & Sustainable Building Design and over 20 years experience in Architecture. Our advice and service is geared around providing solutions for our clients, helping them achieve their goals and input our significant experience to make the process easy, whilst using materials and systems that are readily available.