photos from the both rounds of testing.
First Tophouse Assessments Ltd came 2009-03-30 to do the pressure test plus a bunch of related efficiency measurements/certificates.
The headline permeability figure from Tophouse was 7.21m/h.
Building regs specify a ceiling of 10m/h (or m^3/(m^2.h)), so ours was acceptable even by modern standards.
Tophouse spent a large chunk of the day with me to produce other relevant metrics/certificates, for example the SAP Energy Performance Certificate which for example computed a CO2 emissions figure (1.9t/y) pretty close to the 2.2t/y that I came to based on detailed meter readings.
(I'm quite pleased with our SAP 'B' rating, given that according to Joan Ruddock in the House of Commons 2009-03-20: "... only 30,000 properties in England are at the band B standard.")
In preparing the certificates various parameters of the buildings had to be measured (such as perimeter and window sizes) and estimated (such as window seal tightness and wall composition and U-values) or filled in from supporting tables given typical values for our house's age (1968, SAP 2005 band E) and construction (timber-frame).
For example, the wall was estimated to have a U-value of 0.8W/m^2/K, which now could be bettered by about a factor of two. The downstairs solid floor was estimated to have U-value 0.79W/m^2/K. The roof/loft with ~280mm of fibreglass would have a U-value of 0.16W/m^2/K.
Most heat for solid ground floors is modelled as lost at the perimeter, and our ratio of perimeter to floor area is ~50% (17.4m/38.2m^2).
Tests/results/certificates by Tophouse for us were:
Smoke pencils were used to find leaks with the build over-pressured thus driving the smoke clearly out through the offending leaks (though with underpressure it is easier to feel leaks by hand I think).
Some major leaks found during this process were:
Looking at the internals of the SAP report, in particular the estimates of how much heat energy is being lost where, has made it easier to focus effort and expenditure on the right places.
The total bill from Tophouse was £300 (no VAT).
Next UK Air Testing independently repeated the permeability test on 2009-04-06.
The headline permeability figure from UK Air Testing was 7.11m/h.
The closeness of the result to that from Tophouse Assessments indicates that the calibration and methodology is indeed good enough that either result would have done, and indeed that someone testing their own house could shop around on price confident in an accurate result from any competent assessor.
A smoke pencil was used to help find major draughts/leaks with the fan running, and some were found that had been overlooked before, including:
Taping the airing cupboard door, plus the old vent and piping kitchen leaks, dropped the permeability to 6.29m/h, ie by over 10%. (Just the kitchen leaks taped had permeability down to 6.7m/h.) Uncovering the kitchen (planned) air vents only raised it to 6.6m/h, showing that we had more unplanned than planned air movement in the kitchen for example!
Other leaks picked up were (some new):
A pearl of wisdom from today's tester was that you should regard the internal finish/envelope of each room as the main leak barrier and NOT assume that holes in internal walls (eg for wiring) are not a problem. In our case the biggest leaks are to/from what appear to be interior voids, at least at first blush.
The total bill from UK Air Testing was £195.50 (including VAT).
The permeability figures obtained of ~1470m^3/h exchanged/leaked for a dwelling/house of heated volume ~380m^3 ~190m^2 indicates ~4 ~8 complete air changes per hour (ACH) at 50Pa pressure delta, or ~10 ~20 times the typical Passivhaus n50 value of 0.4/h and more than 6 12 times the Passivhaus n50 limit of 0.6/h.
The obvious action is to buy/borrow and deploy a good foam gun (or more substantial weaponry for bigger holes) and block all the serious leaks, especially those around the kitchen and airing cupboard pipework/services, plus some more delicate resealing of the window in my daughter's bedroom to silence the low whistling sound in strong winds that she objects to. This "retrofitting" should be cheap and easy enough even for me to do, and is classic DIY "weatherization" (US) or "weatherproofing" or "caulking"/"calking", albeit internal.
Some of this may be preempted by larger works such as internal wall insulation which should deal with such problems in bulk.
The old boiler flue/surround from the kitchen, and the foul-air vent which contains other pipework such as overflows, are probably both open to the air on/in the roof and thus providing unwanted venting of the interfloor space to the outside, so finding some way to seal those well would probably pay good dividends, and reinforce gains from sealing the interior leaks to the interfloor void.