PassivHaus


‘What is the benefit of PassivHaus over BREEAM Domestic sustainability standard’?

BREEAM

The Building Research Establishment’s Environmental Assessment Method (BREEAM) is the most widely used building rating tool in the UK. BREEAM Domestic is a relatively new standard used in place of Code for Sustainable Homes, which was scrapped as of 2015.

Unlike the Passivhaus, which is a pass or fail system, it has more of a sliding scale from ‘satisfactory’ to ‘excellent’, where often you get more points if you spend money on additional accessories, i.e. bat boxes/ garden compost bins/ anti-intruder locks/ cycle racks/ etc.

BREEAM Domestic is relatively new and even the most experienced BREEAM Assessors is a little confused about what is required of them. They offer competitive fees and work on many (#MANY) projects like yours. I have never came across an Assessor that was useful to the design process as he/she has no time to actually access the sustainable aspects of your building in practice.

BREEAM Assessors do not give you advice on materials, airtightness or cold bridging; they simply refer you to the BRE Green Guide and ask for third-party thermal performance (SAP) calculations. The SAP technician will give you endless sheets of numbers and no guidance on what to do with them.

The hard task of ‘compliance’ normally falls on the shoulders of the Architect, who tends to treat the process with great irritation and often do not get paid for this additional service.
Basically there is no guarantee that your home will be better from BREEAM assessment. You can find a bit more about BREEAM here

PASSIVHAUS

Passivhaus is a low energy standard that comes to us from Germany. It will give you a good quality build and low energy bills but it typically comes at 5-15% premium.
Builders in the UK are still afraid of getting it wrong and add cost for the ‘unknown’ risk. In my experience, PassivHaus residential buildings take around 3 weeks longer on average to be completed (that is, if the inexperienced builder is being used).

You also need to factor in the cost of a PassivHaus Designer who provides the sustainability assessment, thermal calculations, cold bridging checks and often the site training on airtightness. They are essential to driving the additional costs of your building work down! Experienced PassivHaus designer is key to the process!
The result of this meticulous assessment is that Passivhaus buildings perform as designed, hence the low bills and internal comfort promise. For more information on PassivHaus click here

NO CERTIFICATION

I am personally of an opinion that if you do not have the money to spend on certification, you are better off spending it on your build providing you have a knowledgeable Architect and a good builder! It could cost you thousands to certify a building to BREEAM or PassivHaus standard!

I would be looking for more common sense approach on a low-budget self-builds:
– High levels of insulation (30% above Building regs at least);
– Low airtighness (aim for 1 or at least below 3 m2/m3.hr@50Pa with MVHR and between 5 and 8 m2/m3.hr@50Pa for naturally ventilated buildings);
– Sustainable materials are easy to find online (see BRE Green Guide or simply go to eco material retailers);
– Structure – build in timber and/or laminates to avoid cold bridges as much as possible. If using steel, isolate it using thermal pads;
– Windows – must be good quality, I would recommend triple glazing if you can afford it and always check its air tightness values, i.e. sash window does not get a good air seal because its mechanism doesn’t clamp.

I hope this helps.

For more information or to get a quotation for the Architectural or PassivHaus Designer services, please email me on maiiawilliams@mail.com