Trouble with sub contractors on a price is that they are always in a hurry to go home!

I have two done and both times I was moderately happy as they did offer advice and even helped to trace leeks.

The first guy had loads of trouble as he wasn't expecting a masonry house to so air tight and had to reduce his blower fan aperture several times and slow it down a lot too.

I forgot to seal up the cooker hood duct the first time and found a couple of unsealed service penetrations by listening for the sound of wind whistling through the gaps, noted and sealed later on.

They both drew graphs at various pressures and sent a report

Second guy's result was less than one 0.98

I asked about their worse results and both told me that had been to new houses where their fan could not raise the pressure to 50Pa plenty of poor results.

One problem is that a pass is hopelessly leaky and so their standards are low and OK is not OK

Guy I had, had a TI camera and a smoke stick. Spent the morning here.

Maybe it's best to separate out the diagnosis bit and the testing bit. Make up your own crude fan arrangement to allow finding problems while you're building. No need to make accurate (or any) actual measurements. Then a test once it's built to verify the required level has been reached.

Testing on the final structure is, IMHO, flawed anyway. E.g., you might have areas which are only sealed by the plasterboard with dreadful thermal bypass behind which is, at the end of the process, undetectable and would be very expensive to fix even if it was detectable but would have been trivial to find and sort out if the basic shell of the house had been tested earlier.

So, we scratched around for an air test company. with the builder abroad and really worried that we might fail the test.

I sealed all openings beforehand. Architect arrived to witness his first test on site.

Fan in doorway, computerised read out. Didn't work at first, more fiddling and result just over one. Considering there was nowhere for the air to go, I was disappointed, then I noticed that the seal around the door had blown apart. Bloke basically said, well you've passed by a mile so it doesn't matter. I was too slow and didn't voice my objections, bloke went off, architect (and builder, who phoned up for result whilst on holiday) all very pleased.

Hey ho, I wonder what the real result would have been?

Posted By: Ed Davies

Posted By: dickster… then I noticed that the seal around the door had blown apart …

Yes, I've wondered about that - the test does test the temporary seal made by the blower door but doesn't test the actual seal made by the real door. Not ideal.

Unless you go for dodgy cheap doors you shouldn't have a problem Ed. Our front door and utility room door are almost identical save for a small glazed panel in the front door. I made sure to check the seals on the utility room door with a smoke pen when the house was both pressurised and depressurised and didn't find a hint of a leak.

I'd echo your sentiments about testing the house before the plasterboard is in place so that if there is a problem it can be found and fixed. It did cause us some problems however as the software got upset due to the change in internal volume due to the airtightness layer getting sucked in/blown out. It was also quite scary to witness the pressure put on the foil and the taped joints, it was tight as a drum at 50Pa, but thankfully all held together, the tester told me he had left another house in tatters when testing in similar circumstances for a "professional" builder.

http://www.greenbuildingforum.co.uk/forum114/comments.php?DiscussionID=7396&page=1

Difficult to tell without a proper performance curve (flow rate against back pressure) but if it was 25% efficient it would produce roughly 50 Pa at the rated flow rate so it's probably in the right ballpark.

Posted By: Chris P BaconIt was also quite scary to witness the pressure put on the foil and the taped joints, it was tight as a drum at 50Pa, but thankfully all held together, the tester told me he had left another house in tatters when testing in similar circumstances for a "professional" builder.

That's also scary in a different way - windy weather can produce a lot more than 50 Pa. I wonder how many installations pass the pressure test then are reduced to tatters (unseen behind the plasterboard) by the next winter storm.

E.g., 20 m/s (only a Beaufort scale “fresh gale”) would produce a dynamic pressure of ½ρv² = 0.5 * 1.3 * 20 * 20 = 260 Pa and that's just the steady pressure without the effects of momentum and gusts.

I have been told that we achieved just over 1, not bad given the MVHR was not sealed and there were obvious leaks around the fan itself, paper report to follow. Tester thinks it is an amazing result, but I feel quite disappointed. The build is better than that, but I don't know by how much, nor do I know if there are any leaks we could fix.

Other than self satsfaction, is there any thing to gain from another test? Would a DIY test be able to locate leaks in such an air tight build? Depressure at max fan speed and feeling for leaks wth a hand? Worth hiring someone specfically to run the fan while we look for leaks rather than just generate a number for building control? Should I wait a year and test then showing how the building is settling in too?

If it had been below 1 then the beers would be on me!

Posted By: GreenfishI have been told that we achieved just over 1, not bad given the MVHR was not sealed and there were obvious leaks around the fan itself, paper report to follow. Tester thinks it is an amazing result, but I feel quite disappointed. The build is better than that, but I don't know by how much, nor do I know if there are any leaks we could fix.

I'm trying to organize my first test. Who did your test, so I can avoid them? (whisper if you don't want to publically shame). I think it is key to check up front that they know how to do a PH test rather than a building regs one. Can you get him to come back?

Other than self satsfaction, is there any thing to gain from another test? Would a DIY test be able to locate leaks in such an air tight build? Depressure at max fan speed and feeling for leaks wth a hand? Worth hiring someone specfically to run the fan while we look for leaks rather than just generate a number for building control? Should I wait a year and test then showing how the building is settling in too?

I think it's definitely worthwhile to have access to a fan for leak location. Crank it up to max and use a smoke pencil or cigarette or back of the hand etc etc. I figured it was cheap and easy enough to build a simple system to help with leak location. Cetainly cheaper than paying for somebody to come in with their own kit, although you should get the benefit of their experience if you do the latter. The ability to repeat tests later is also something I like the idea of my own lash-up for.

Posted By: fostertomA sail generally only experiences forces in one direction; a house's membrane experiences frequent fatiguing pressure reversals, with a yank every time.

Unless I misunderstand then there won't be "a yank" on the membrane unless there is a void on one side. A membrane sandwiched between solid layers of construction just won't experience anything like the same forces as a sail in the wind.

Posted By: djhI'm trying to organize my first test. Who did your test, so I can avoid them? (whisper if you don't want to publically shame).

Used a local guy, you should be OK if not in my part of the world. To be fair he was nice enough, just didn't get (no matter what I said) that I was interested in more than passing. In 7 years of testing he said I was one of the few even interested in the test process. Mostly he was just worn down by the abusive atttude of most builders and architects he encountered daily. Great shame, and my mistake for not putting my test requrements e.g. seeking leaks even if they are small, and nialing as small a value as possible, on paper as contractual.

I think it is key to check up front that they know how to do a PH test rather than a building regs one. Can you get him to come back?

Yes, simply telling them my design aims for air tightness was not enough. Find someone intereted in their job rather than jaded. Sure he would come back if I paid him, but I doubt he has accuracy in his skill set.

Have found a place where I can hire a fan for leak testing, but not the manometers, software etc. and didn't get the price. However they advsed that seeking leaks in such an air tight build would be rather futile. Anyone agree?

@Greenfish you can probably estimate what the savings would be if you were to say halve your air tightness result. Although I'm not sure how you get figures for hourly wind speeds at your location and then relate them to the temperature differential at the same time. Sounds like a job for ST!

Maybe just take a worst case scenario of a cold and windy day and figure out what the potential difference will be.

That would be an interesting exercise.

Posted By: Chris P BaconSounds like a job for ST!

Greenfish is local too, and the weather data is easy to get hold off (and I can take down my new weather station and bring that along).

I think we had a thread on here about DIY testing and our old mate J S Harris told us how to make a manometer and control a fan.

Posted By: Chris P BaconI was thinking more along the lines of a theoretical calculation ST.

Like I did here with windspeed.
http://www.greenbuildingforum.co.uk/forum114/comments.php?DiscussionID=11624&page=1

Posted By: Chris P BaconHow many kWhrs that represents calculated for both 1ACH and 0.5ACH so Greenfish (and others) can figure out how much effort it is worth going to to achieve the absolute best result possible.

Sadly perhaps, the reason quoted for such a tight airtightness level in PH isn't to do with the energy or cash saved directly. The point as I understand it is to avoid drafts and to maintain internal surface temperature everywhere. That in turn allows you to reduce the internal air temperature by a degree or two whilst maintaining the same level of comfort, and that is what saves the energy and cash.