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Submit plansHi, We finished a self-build project last year and we’re only now getting round to applying for completion. Building standards state they require a Q50 airtightness result between 5 and 7, our test has come in at 2.79. I’ve been informed that it’s not as simple as putting a couple of vents in the wall and that we may have to strip plasterboard around walls and remove tape/seal around junction with walls and floor. In the plans the SAP calculations state a figure of 7 for the Q50.
Unfortunately due to disputes with the architect we parted ways before the end of the project.
Does anyone know of any less drastic way of getting the Q50 figure up to 5?
Thanks
I’ll confess that this is a new one on me and I’ve had to ask my professional contacts for their take on it. It seems a real shame to have to take such retrograde action when a house has been built to such high standards, but it points out the perils of building to high levels of airtightness without professional guidance. I’m wondering if parting with the architect at a crucial stage has led to this situation because no designer or architect I know would have sanctioned building to this level of airtightness without specifying a mechanical ventilation and heat recovery (MVHR) system to maintain the levels of fresh air inside the home. As you have no doubt discovered, retrospectively installing MVHR is expensive and disruptive which is why it needs to be considered at the early stages of design.
My building control friend Paul Kalbskopf has suggested considering installing stand-alone units as a possibility to discuss with building control. I also spoke to Mike Lawrence at Total Home Environment who is an expert in MVHR. He points out that simply installing MVHR will not address the airtightness levels, but would manage the airflow in a relatively airtight house like yours. He suggests revisiting the SAP to see if there is any way of adjusting some ventilation details to comply.
Mike Hardwick (Build It expert)
