Air Tightness Test - poor result

[mike2016]

Got a 1.56 on the blower door test. Disappointed as was aiming for 0.6. I did the membrane and tape (no one else to blame) but nearly all the windows and doors had issues from the smoke test. I used OSB with wood screws around the window straps to provide a level base for the plasterboard in the reveals. My guess is this is where the smoke was able to get through (the screw penetrations). I assumed the Intello Plus would have been able to seal around the screw but I have my doubts now. I can apply a liquid seal around the OSB and the screw head to help or remove and seal the hole with tape and figure our the plasterboard approach later. 

The plasterboard will also need to screw through the OSB so could make this worse. 

Any advice? Thanks! 

 

[Post and beam]

Regardless of the OSB, what, if anything, are you using at the interface shown by my yellow line? This is where you would put airtight tape 

[mike2016]

I have a edge tape at this location, partially covered by the OSB but I'm happy that junction is secure......

[ProDave]

Is the "poor" score really an issue?  Are you hoping for passive house certification.

 

I too got a poor score of 1.4 without being able to pinpoint where the leak(s) were.

 

But the end result is still a very low energy house and an as build SAP score of A94 so not entirely shabby.

[nod]

Hopefully no one opens a window when you move in

Then you will really loose your shit 😂😂

[mike2016]

Yes and no. I can live with a 1.56 but this is the only chance I'll have to do something about it. I'm trying to figure out a way to get an improvement to at least < 1 but the screw penetrations have me at a loss. I can seal around the OSB with Pro Clima Aerosana Visconn Fibre and the screw head also and use glue to fix the plasterboard to the OSB, that way I can test the result with a home made fan and smoke box. Bit of a pain though! Still mulling the result but that was only yesterday so yes, may just shrug and get the house built......

[Thorfun]

39 minutes ago, ProDave said:

Is the "poor" score really an issue?  Are you hoping for passive house certification.

 

I too got a poor score of 1.4 without being able to pinpoint where the leak(s) were.

 

But the end result is still a very low energy house and an as build SAP score of A94 so not entirely shabby.

+1.

 

1.56 isn't poor! just compared to some on here and i guess it's poor if aiming for 0.6ACH but it's all relative. we got a score of 1ACH and it was my target so i was happy. i probably could've done more but life's too short for me to worry about the small-ish difference it would've made getting it down further.

[ProDave]

I would be surprised if it was screw penetrations.

 

To allow yourself some investigation time can you rig up your own blower door?  I used some OSB, some cardboard, an old desk fan and lots of duct tape.  This won't get you a reading but will allow you to spend as long as you like going round with something that makes smoke, e.g. Joss sticks, to investigate where the leaks are.

[Thorfun]

1 minute ago, ProDave said:

I would be surprised if it was screw penetrations.

again i agree!

 

all my service cavity battens are screwed through our Intello Plus and so there are a lot of screw penetrations.

[mike2016]

Was thinking of getting a fan / smoke setup for exactly this. Will have a look around this evening before the storm hits and figure out a rig to let me do further testing before spending anything more on this. Cheers!

[JohnMo]

4 hours ago, mike2016 said:

Got a 1.56 on the blower door test.

From photos that is obviously just a preliminary test. 

 

So as not your final test, (as the plasterboard and second fix not complete), you have plenty of time to get things fixed to your liking.

[saveasteading]

5 hours ago, mike2016 said:

Got a 1.56 on the blower door test.

 

5 hours ago, mike2016 said:

I used OSB with wood screws

1.56 is ok and multiple times better than a commercial new house (they do one up for  a test and ignore the others and give them all the pass score).

It is not the screws. it will be at corners and ends of boards.

Plasterboard will help, not make it worse. You could put some mastic under the boards near these corners etc.

 

2 hours ago, nod said:

Hopefully no one opens a window

You have fans in the wc and kitchen...a 110mm hole direct to outside.  We all do. But they suck the air from draghy windows/ under doors which you have nearly sealed. Relax.

[ProDave]

6 minutes ago, saveasteading said:

You have fans in the wc and kitchen...a 110mm hole direct to outside.  We all do. But they suck the air from draghy windows/ under doors which you have nearly sealed. Relax.

If you are hoping for an air test of 0.6 I very much doubt you have anything other than MVHR.

 

One characteristic of an air tight house, is you can open one window or one door and you will get very little draught.  It is only when you open 2 at the same time a howling gale goes through.

 

Contrast that to out previous house.  You opened the front door on a windy day and internal doors would blow shut or open as the howling gale entered through the door and rushed towards any of the extract fans in bathrooms, kitchen or utility, the cat flap, or the window trickle vents, or up the chimney via the stove that took it's air from the room, or out through the vent built into the hearth.

 

I am convinced mvhr and eliminating all those deliberate big holes in a building would work wonders even in a house that is not particularly air tight.

[mike2016]

MVHR is going in for sure. Have both pipes installed but closed with plastic bags and duct tape. I have an office fan to keep me cool in the summer in my rental so plan to join this to one of the ducts using intello & duct tape (!) and pressurize the house with it. I've just ordered a smoke pen with a small wick I can light / extinguish to pinpoint exactly where the leaks are. The tester did say the plasterboard would help and to seal around the floor as it will be a few mm off the concrete but there are going to be electrical backboxes etc / holes in this so it's not a perfect layer and I won't be air sealing those. It will help though! 

Building Regs over here is below 7 is a pass!! They only have to test 1 in 10 houses in a development though so the rest have gales blowing through them , meant to be "A" rated too!! 

The tester said one guy got a result of 0.24 and the final test was 0.28, he went nuts, demanded to find out why!! I'd be happy with any improvement but taking the time now to figure this out works for me! 

Thanks all!! Great advice and anecdotes as always! 

[saveasteading]

1 minute ago, ProDave said:

mvhr and eliminating all those deliberate big holes

I am a sceptic on mvhr. This may be because the early iterations (or some) were clearly flawed, with poor heat transfer and some short circuiting of the air.  Or was it hat the reps didn't understand their products?

 

Has anyone done a proven comparison of a control v mvhr house?

 

I did a quick, theoretical  assessment once and made it that mvhr would payback in 12 years, after including the power input.

[mike2016]

Good direction to question but I installed one into the upstairs of my old house and gained experience for my build but also much better quality of air in my bedroom at night which would reach 3-4,000 ppm of CO2 at night without it. I lived beside a busy road so not always possible to open a window (or it was too cold). I'd wake up gasping. Never had a bad night sleep with it installed. I value a good nights rest so it was worth the investment for that reason for me. Hence doing it in new house too! 

[ProDave]

It is all relative.  I was disappointed with my 1.4 test but the guy doing the tester nearly wet himself he was so delighted with the result, the best he had seen.  I also got the impression my BC inspector had never seen an EPC A before.

 

As to whether mvhr works to save heat?  All I know is in Scotland if your air test is less than 3 you must fit mvhr.  Compared to the old uncontrolled ventilation regime with lots of individual holes in the building, it is marvellous.

[saveasteading]

10 minutes ago, ProDave said:

if your air test is less than 3 you must fit mvhr. 

We aren't testing the steading. 'Reasonably practicable' applies for conversions.  I  way its a shame as I think it will be a very god score, notwithstanding the very high external wall and roof areas (central courtyard) and the stone external walls retained to 3/4 of it.

 

I didn't know this about being too airtight. It seems o be 5 not 3.

 

BUT don't we seal and close the vents before testing, then open them for real life? Will this need 2 tests?

 

Lower air infiltration rates, of less that 5m³/h.m² @ 50 Pa, may give rise to problems with internal air quality and condensation unless this is addressed through planned ventilation.

[Post and beam]

You could always go nuclear and get the mist system. This will find the holes and plug them.

 

https://www.aerobarrieruk.co.uk/

 

 

[Nick Laslett]

@mike2016 thank you for posting your results. Good luck with making any improvements. 
 

I’m sure there are some good posts here already about DIY air testing. It is a shame to pay twice for an air test if it can be avoided. But please keep us updated if you do get another test done. 
 

It would be good to know what else you could do, if you have already taped a membrane over the window interface?

 

 

[ProDave]

2 hours ago, saveasteading said:

We aren't testing the steading. 'Reasonably practicable' applies for conversions.  I  way its a shame as I think it will be a very god score, notwithstanding the very high external wall and roof areas (central courtyard) and the stone external walls retained to 3/4 of it.

 

I didn't know this about being too airtight. It seems o be 5 not 3.

 

BUT don't we seal and close the vents before testing, then open them for real life? Will this need 2 tests?

 

Lower air infiltration rates, of less that 5m³/h.m² @ 50 Pa, may give rise to problems with internal air quality and condensation unless this is addressed through planned ventilation.

A near neighbour planned on DMEV and had pretty well installed that, but when his air test came in at less than 3 he was instructed by BC that full MVHR was required.

[Roger440]

3 hours ago, saveasteading said:

I am a sceptic on mvhr. This may be because the early iterations (or some) were clearly flawed, with poor heat transfer and some short circuiting of the air.  Or was it hat the reps didn't understand their products?

 

Has anyone done a proven comparison of a control v mvhr house?

 

I did a quick, theoretical  assessment once and made it that mvhr would payback in 12 years, after including the power input.

 

So what do you do instead of MVHR?

[Post and beam]

28 minutes ago, Roger440 said:

So what do you do instead of MVHR?

i am curious as well. In Hertfordshire, and i doubt its different anywhere else in at least England, MVHR is mandated below a score of 3.

[Benpointer]

3 hours ago, saveasteading said:

I am a sceptic on mvhr. This may be because the early iterations (or some) were clearly flawed, with poor heat transfer and some short circuiting of the air.  Or was it hat the reps didn't understand their products?

 

Has anyone done a proven comparison of a control v mvhr house?

 

I did a quick, theoretical  assessment once and made it that mvhr would payback in 12 years, after including the power input.

Of all the 'eco' things we did in our last house (amajor renovation) - triple-glazing, MVHR, ASHP, UFH, PV, Solar HW, masses of insulation...  Of all those things, MVHR was number 1 on the list for our forthcoming self-build.  Not for payback but for comfort.

Edited Thursday at 22:34 by Benpointer

[Post and beam]

5 minutes ago, Benpointer said:

Not for payback but for comfort.

Agree, not everything we buy needs to have a return on investment in cash terms.