Another air test – 0.37ACH

After a full on week filling the narrowest of gaps underneath all the external door thresholds with silicon, more taping and more filling (the edge where the concrete slab meets the threshold), today we had our second air test.

Calculating internal volumes of the house is pretty complex. Thanks to our Passivhaus consultant Rod, who carefully calculated the whole house volume to be 613.47 m3. Our air test result achieved 0.37 ACH.

This now means we can say with more confidence that we are hoping to achieve the certified Passivhaus standards.

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Warmcel Insulation

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7,680 kilos of Warmcel cellulose fibre insulation (recycled newspaper) is being pumped under pressure into the external walls and roof of the house this week.

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Warmcel is insulation for timber framed buildings. The manufacturer states that ” Sustainably manufactured Warmcel provides superior performance that offers industry-leading thermal performance, ensuring your building’s U-values don’t just meet baseline building regulations, but go on to exceed them.
Warmcel cellulose fibre has a high specific heat capacity and high insulation value offering any home significant thermal mass and excellent heat retention. A Warmcel insulated home is designed to hold heat for a long time and to minimise daily temperature fluctuation- an essential quality for a comfortable environment.”

Stage Four – Air Testing and Insulating

The first air test was carried out on April the 1st 2016.

It acheived 0.72pa ACH50. To reach Passivhaus standards it will need to be below 0.6pa.

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The air test was carried out on the DWD layer which is the external skin of the structure.

We spent most of the Easter weekend taping the internal membrane and sealing around the Windows. We ran out of tape on the Saturday afternoon and had to make a quick dash (1hour each way)to Back to Earth in Exeter for a box of Udi tapes. Thanks to Chris Brookman for opening up over the bank holiday weekend. We think the Udi tapes have more stickiness than the Tescon tapes.

Unfortunately we ran out of time before the pre-booked air test date, and we knew there were three windows that were not properly sealed. We also heard the ground floor sliding windows whistling during the test and we noticed that they too had not been properly sealed with silicon.

Therefore we are currently taping the internal Intello vapour barrier which we hope will create further air tightness. We feel confident that with the windows sealed and the additional air tight layer we should achieve the passivhaus requirement on the next air test.

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We underestimated the amount of time it takes to hang, staple and tape the internal membrane, along with underestimating the amount of tape needed!