Air pressure test
Discussion
I have an air pressure test booked in on friday for our new build (one of the final loops to jump through before sign off), normally you have an idea about how something is going to perform prior a check, but on this I have no idea!
Apparantly I need to reach an air permeability rate of 9
Anyone know what kind of trouble to expect? How air tight do things need to be, I am of course going to be armed with a s
t load of silicon sealant, but would rather not apply to everything as I think it looks crap.
Looking at the web sites they suggest sealing things like light fittings and sockets, so on the former how are you supposed to change the bulbs, and on the latter wont the air just go through the plug holes anyway?? I have not done either, and I have the cardinal sin of dot and dab plaster!
Just wondering what the 'absolute musts' are for sealing is so I can do some in advance, or with a '9' rating will I be able to leave a window open and still pass!
Apparantly I need to reach an air permeability rate of 9
Anyone know what kind of trouble to expect? How air tight do things need to be, I am of course going to be armed with a s
t load of silicon sealant, but would rather not apply to everything as I think it looks crap.Looking at the web sites they suggest sealing things like light fittings and sockets, so on the former how are you supposed to change the bulbs, and on the latter wont the air just go through the plug holes anyway?? I have not done either, and I have the cardinal sin of dot and dab plaster!
Just wondering what the 'absolute musts' are for sealing is so I can do some in advance, or with a '9' rating will I be able to leave a window open and still pass!
Went through this bullst 
in November last year on our self build. All window trickle vents shut, chimney blocked up, pipe exit/entries foamed/siliconed, it was a pain in the arse to be fair. The worst places for loss were behind skirting and architrave where the plasterboard dot and dabbing hadn't fully enveloped the board thus allowing some air to get up behind it.
in the end we achieved 7.75 I think, the building regs pass figure is 10 but you say you need 9 which is probably from the original SAP calcs.
Good luck!
t in November last year on our self build. All window trickle vents shut, chimney blocked up, pipe exit/entries foamed/siliconed, it was a pain in the arse to be fair. The worst places for loss were behind skirting and architrave where the plasterboard dot and dabbing hadn't fully enveloped the board thus allowing some air to get up behind it.in the end we achieved 7.75 I think, the building regs pass figure is 10 but you say you need 9 which is probably from the original SAP calcs.
Good luck!
A test figure of 9 is not difficult to achieve if you built with airtightness in mind, but it's by no means a walkover and if you didn't build with airtightness in mind, you're going to have fun... stable door and bolted horse, I'm afraid.
If you e-mail me via my profile, I can mail you a bunch of guidance that you might find useful (or depressing, depending on how careful your build was...).
We regularly achieve half your target figure and have occasionally built houses so airtight that they failed for being to low, but that's with a great deal of attention to detail and experienced Site Managers.
It's all a load of bks, by the way... if you go back and test a house that's been lived in for a year, you'll get a dramatically lower test figure due to shrinkage cracking, holes drilled in walls and ceilings, etc., which is one of the reasons by the energy consumption estimated by the SAP calculation process is often out by 35-40%.
If you e-mail me via my profile, I can mail you a bunch of guidance that you might find useful (or depressing, depending on how careful your build was...).
We regularly achieve half your target figure and have occasionally built houses so airtight that they failed for being to low, but that's with a great deal of attention to detail and experienced Site Managers.
It's all a load of b
ks, by the way... if you go back and test a house that's been lived in for a year, you'll get a dramatically lower test figure due to shrinkage cracking, holes drilled in walls and ceilings, etc., which is one of the reasons by the energy consumption estimated by the SAP calculation process is often out by 35-40%.Sam_68 said:
A test figure of 9 is not difficult to achieve if you built with airtightness in mind, but it's by no means a walkover and if you didn't build with airtightness in mind, you're going to have fun... stable door and bolted horse, I'm afraid.
If you e-mail me via my profile, I can mail you a bunch of guidance that you might find useful (or depressing, depending on how careful your build was...).
We regularly achieve half your target figure and have occasionally built houses so airtight that they failed for being to low, but that's with a great deal of attention to detail and experienced Site Managers.
It's all a load of bks, by the way... if you go back and test a house that's been lived in for a year, you'll get a dramatically lower test figure due to shrinkage cracking, holes drilled in walls and ceilings, etc., which is one of the reasons by the energy consumption estimated by the SAP calculation process is often out by 35-40%.
Oh crap! build definatly did not have air tightness in mind (I was the PM with no build experiance!)If you e-mail me via my profile, I can mail you a bunch of guidance that you might find useful (or depressing, depending on how careful your build was...).
We regularly achieve half your target figure and have occasionally built houses so airtight that they failed for being to low, but that's with a great deal of attention to detail and experienced Site Managers.
It's all a load of b
ks, by the way... if you go back and test a house that's been lived in for a year, you'll get a dramatically lower test figure due to shrinkage cracking, holes drilled in walls and ceilings, etc., which is one of the reasons by the energy consumption estimated by the SAP calculation process is often out by 35-40%.Just to compound it, we have been living in the house for over a year now so lots of nails in the walls!!
You should have mail!
Our builders have managed 2.4 with a traditional timber frame house, but we're hoping to get near 1 for ours. There again, we built with airtightness in mind - no trickle vents, no air bricks and even a room-sealed stove. How close we will get is unknown though, as we've used a few suppliers who don't necessarily design their products with air tightness in mind.
You loose about a third of your heating bill to air leakage on a modern standard home, so there is a good case for saving money if you can pay attention to the details.
You loose about a third of your heating bill to air leakage on a modern standard home, so there is a good case for saving money if you can pay attention to the details.
Dave_ST220 said:
Aren't these draft free places in danger of rotting though? No air flow, where does any moisture go?
We have a ventilation system - so relatively unused rooms still get fresh air changes, and we don't get condensation in humid rooms like bathrooms and kitchen. The philosophy is 'build tight, ventilate right' - which I'd be the first to say is still rather experimental, but has to be better than the traditional way of making a house as leaky as a sieve and hoping that some fresh air will get to the right places.So far, the house always feels fresh and very comfortable - the big test will seeing if my sister in law can stay without dosing up on allergy tablets.
Tuna said:
Our builders have managed 2.4 with a traditional timber frame house, but we're hoping to get near 1 for ours. There again, we built with airtightness in mind - no trickle vents, no air bricks and even a room-sealed stove. How close we will get is unknown though, as we've used a few suppliers who don't necessarily design their products with air tightness in mind.
You loose about a third of your heating bill to air leakage on a modern standard home, so there is a good case for saving money if you can pay attention to the details.
I hope you have mechanical ventilation or that will be horrid to live in. We regularly achieve between 4-6 and my own house I'm targeting 6 as any tighter and the space feels horrible to occupy. We once built a commercial office to 2 and had to go back and double the number of trickle vents as it was too airtight and we had huge problems with condensation.You loose about a third of your heating bill to air leakage on a modern standard home, so there is a good case for saving money if you can pay attention to the details.
If you struggle get a LOT of people to stand in the lounge that will help the result.
To the OP: I'll try to get the information I promised off to you tonight; I can't access my personal e-mail from the office, so it will be later on, though.
Timber frame is a lot easier to achieve good airtightness with; to consistently get below 3.5 with traditional, you have to take extreme care and additional measures... for example you can forget about dry lining on its own; you need a parge coat on the bare blockwork just to seal it, before you dry line.
I agree Fish's comments and even with MVHR, you'll find it's pretty horrible to occupy at those levels of airtightness. The basic problem is that you're replacing a structure that leaks a little bit of air from lots of different places with one that's completely airtight and circulates air through one or two vents per room. The air flow isn't as evenly distributed and you get a lot of dead spots, particularly when you introduce furniture and furnishings. And then there are the long-term maintenance issues....
And yes, Dave, you do tend to get more problems with condensation for the same reason (inconsistent circulaton).
I'm with Fish - I'd prefer to draw the line at 4-6.
Depends whether you value your health more than your heating bills, though....
Fish said:
Tuna said:
Our builders have managed 2.4 with a traditional timber frame house, but we're hoping to get near 1 for ours...
I hope you have mechanical ventilation or that will be horrid to live in. We regularly achieve between 4-6 and my own house I'm targeting 6 as any tighter and the space feels horrible to occupy.I agree Fish's comments and even with MVHR, you'll find it's pretty horrible to occupy at those levels of airtightness. The basic problem is that you're replacing a structure that leaks a little bit of air from lots of different places with one that's completely airtight and circulates air through one or two vents per room. The air flow isn't as evenly distributed and you get a lot of dead spots, particularly when you introduce furniture and furnishings. And then there are the long-term maintenance issues....
And yes, Dave, you do tend to get more problems with condensation for the same reason (inconsistent circulaton).
I'm with Fish - I'd prefer to draw the line at 4-6.
Depends whether you value your health more than your heating bills, though....
Sam_68 said:
I agree Fish's comments and even with MVHR, you'll find it's pretty horrible to occupy at those levels of airtightness. The basic problem is that you're replacing a structure that leaks a little bit of air from lots of different places with one that's completely airtight and circulates air through one or two vents per room. The air flow isn't as evenly distributed and you get a lot of dead spots, particularly when you introduce furniture and furnishings. And then there are the long-term maintenance issues....
We'll see - so far it's a pleasure to occupy, though we haven't done a winter which will be the acid test. We've taken a belt and braces approach though. All of the windows have a trickle position and the vent system is quite well sized for the property. The point is that we have the option as to how we ventilate. Unlike the passivhaus crowd, we've aimed for a house we can control, rather than a house that dictates how we live.For a traditional 'leaky' house, if you're getting down to lower single figures without designed ventilation you run the risk that all of your ventilation is coming from a few points, or the windward side of the house - which leaves some rooms with 'dead' air, or bathrooms feeding neighbouring rooms with unwanted humidity. You have to over ventilate to allow for the 'worst case' rooms.
Tuna said:
You have to over ventilate to allow for the 'worst case' rooms.
Ironically, I'd see that as one of the major disadvantages of the high air-tightness/MVHR route; you need to boost the circulation of the MVHR sufficiently to circulate enough air throughout the room, which means that in order to circulate enough through the 'dead spots', there are areas where the localised flow is much higher than it needs to be. We've had complaints due to backgound noise and draughts with MVHR, and condensation/mould problems can be very difficult to predict (even in identical house types, with very similar air test results).
The other problem with MVHR is that performance deteriorates with age (contamination building up within ductings and within the furnishings/decorations within rooms themselves, people not changing the filters as regularly as they should, motor performance dropping off, etc.), so even if it works at day one, you can't really be confident that the environment will remain acceptable 10 years down the line.
Don't get me wrong; we're fitting MVHR with increasing regularity these days (as a means of compliance with the higher levels of Code), but we're suffering issues already and I'm far from confident that the technology won't turn round and bite the industry in the arse, just as so many other 'clever' ideas have done in the past.
Edited by Sam_68 on Tuesday 27th July 19:40
eldar said:
Can someone explain exactly what this air pressure test is, and why? Sounds like hermetically sealing a house, but I'm sure it isn't that simple...
Basically, you pressurise the house by bolting a bloody great fan to the front door via a duct with seals on it, then measure how fast it loses pressure.To the OP: YHM.
Sam_68 said:
eldar said:
Can someone explain exactly what this air pressure test is, and why? Sounds like hermetically sealing a house, but I'm sure it isn't that simple...
Basically, you pressurise the house by bolting a bloody great fan to the front door via a duct with seals on it, then measure how fast it loses pressure.To the OP: YHM.
Sam_68 said:
Don't get me wrong; we're fitting MVHR with increasing regularity these days (as a means of compliance with the higher levels of Code), but we're suffering issues already and I'm far from confident that the technology won't turn round and bite the industry in the arse, just as so many other 'clever' ideas have done in the past.
It seems to me that, as with many other technologies, we're behind other nations - our climate is such that we've never really been under pressure to properly solve heating, cooling and so on. Take a look at Canada though, and they've been sealing up their homes for years. As a result, MHVR is better understood and enormously cheaper over there - after all, it's just a fan in a box. Talking with Canadian builders and home owners, I've fairly confident that it can work well. You're right though that the UK is on a learning curve and there will undoubtedly be cases where MHVR 'goes wrong', I'd also steer clear of social housing and situations where the owners don't actually want MHVR - it'll almost certainly end up clogged up, switched off or broken.
In fact we had been looking at passive ventilation - I share your concerns about long term reliability, but our house design would never be suitable. In the end I did a lot of research on how well mechanical systems performed before going down that route.
eldar said:
Ah. Sounds daft enough to be some sort of green initiative. What does it achieve, apart from a build up of CO2 and Radon and a certificate?
It predates the current green fanaticism. A draughty house is cold, uncomfortable and expensive to heat. To work out the energy efficiency of a house you start with the levels of insulation in walls, floor and roof, and the air leakage.Particularly since we've been building homes down to a budget, there's a huge temptation for builders to make do with the minimum necessary - single brick walls and no insulation in the roof. Building regs try to prevent the worst excesses, and over the years have got tighter and tighter. Without the tests, two apparently identical houses can cost massively different amounts to run.
Tuna said:
eldar said:
Ah. Sounds daft enough to be some sort of green initiative. What does it achieve, apart from a build up of CO2 and Radon and a certificate?
It predates the current green fanaticism. A draughty house is cold, uncomfortable and expensive to heat. To work out the energy efficiency of a house you start with the levels of insulation in walls, floor and roof, and the air leakage.Particularly since we've been building homes down to a budget, there's a huge temptation for builders to make do with the minimum necessary - single brick walls and no insulation in the roof. Building regs try to prevent the worst excesses, and over the years have got tighter and tighter. Without the tests, two apparently identical houses can cost massively different amounts to run.
Sam_68 said:
eldar said:
Can someone explain exactly what this air pressure test is, and why? Sounds like hermetically sealing a house, but I'm sure it isn't that simple...
Basically, you pressurise the house by bolting a bloody great fan to the front door via a duct with seals on it, then measure how fast it loses pressure.To the OP: YHM.
Really wish I had this before we built, but i guess you live and learn, yet another piece of experiance slides into place ready for the next time we build...
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