Prelim Air test

[crispy_wafer]

Just had a prelim air test completed, as I’m just finishing up, or so I thought first fix ready for plasterboard.  Std brick and block build.  And the result wasn’t great tbh so I wont publish it.  Filled the house full of smoke, reversed the fan to try and ID the areas for attention…

 

Windows, all taped up on perimeters, but the units themselves leak air in the corners, most if not all suffer from this, and my big gable window which comprises of 8 window units leaking along frame joints where attached to next frame  - not happy at all with this.

 

Restraint straps, air making its way down back of restraint strap between blocks and strap.

 

Handful of small holes, and the odd crack in mortar that I’d missed.

 

Big fist sized hole into the cavity I’d missed behind a steel into the cavity - Doh, poor attention to detail!

 

And the mvhr unit, I taped off before the manifolds, maybe I needed to tape off at the building inlet and exhaust, as smoke billowed out the vents, are the units sealed up by design or are they quite leaky?

 

To be fair the company I used (found them on the internet) were spot on, walked me around and helped identify the areas for attention.  My local chap wasn’t interested in doing a test at this stage…

 

£250 quid well spent, even if result was poor.  Now I’ve seen it done, I need to build a rig to replicate.

 

Now I’m going to have a cup of tea, and think about the challenges that lay ahead.

[Kelvin]

Apart from the windows the rest of it is easily fixable so you know you can significantly improve it. My first test result was pretty reasonable and was able to significantly improve upon that for the final test. (0.98 to 0.4) so was money well spent. Doing the air tightness was the bit of my build I enjoyed the most. 

Edited June 21 by Kelvin

[crispy_wafer]

Yes, that’s exactly how I’m looking at it, I’m going to fix the obvious then fetch an industrial drum fan from screwies or machine mart and set to.

[JohnMo]

1 hour ago, crispy_wafer said:

The mvhr unit, I taped off before the manifolds, maybe I needed to tape off at the building inlet and exhaust, as smoke billowed out the vents, are the units sealed up by design or are they quite leaky

I just taped the inside terminals during our final air test. And I think the mvhr units leak like sieves. I have two of them.

 

Get a tub of airtight paint on stuff and airtight foam, that will fix mist things except the mvhr units.

[jack]

1 hour ago, crispy_wafer said:

Now I’ve seen it done, I need to build a rig to replicate.

There've been discussions on here doing this with a scrap electric radiator fan.

Mount it to a frame, add a flexible surround (that you can tape to a window or a door), 12 V power supply (ideally variable), and a pressure guage, and you're set.

[RobLe]

I’ve done this before, and have a set of recommended parts - links below to a suitable fan, power supply, and differential pressure sensor, total under £200.  You can halve that cost by using a car battery charger and no measurement.

https://www.ebay.co.uk/itm/171452099291?itmmeta=01HPJ04NFJ122390GS5BHYCSTA&hash=item27eb576adb:g:AlsAAOSwFLBabz6P&itmprp=enc%3AAQAIAAAA0MHDPIuVE6xMauIT%2B2m3GgQGT8tYsJluxspKLHSwqw2b%2F%2BOcaIly6fBGJylxh3zb5Jt%2BiqjJU5XVvqa3u%2FGMfqCwPjrLEMb5lBzMdLjDfJaGcBD9prP5gR7rYGam3WEHjv5VII7atBOJ1Unhve0fvtuur%2Bo265pYJwGbp2rnHX06VlE%2FewjhoSs4bRG1t%2BVUnBzbF13HZ%2FF3YP7vcD3wY6utJXhe6t2NLy10Vn%2Fn1EUdVjVhKb41RcAUTjvMW8GNMdSgeSgJzKTo1gIgBqDsLTo%3D|tkp%3ABk9SR-jXksC0Yw

 

https://www.aliexpress.com/item/1005003681719599.html?gatewayAdapt=glo2esp

select 15V 20A variant

 

https://www.aliexpress.com/item/1005005320909441.html?spm=a2g0o.order_list.order_list_main.15.44d11802qTJLEi

 

Using those parts, I got the flow versus voltage and pressure relationship below.  Of course, it won’t be super accurate - but what do you expect for £200 of bits?

 

 

Edited June 21 by RobLe

[crispy_wafer]

Thanks @RobLe you've gone above and beyond with the links.  I've picked up a fan from machinemart this aft, and ordered another couple of tubs of soudatight.  I'm just constructing something to block up a window opening, when I've done that, I'll depressurise and wage war on sealing what I can.

 

The main problem was obviously the fist sized hole behind a steel into the cavity that I'd just overlooked.  I've filled that now, just needs trimming back painting and taping over.

 

I'm not sure how much of a culprit the mvhr system is, next time I'll disconnect from the wall outlet and seal at that point, taking the chassis and any internal leakage points out of the equation entirely.

 

The restraint straps will get a good globbing all over with soudatight and also the point at which they disappear under airtight tape.

 

The roof joints to the walls have/had all been taped, these will also get a good globbing over with airtight paint, paying particular attention to where the tape bridges mortar joints in the blocks.

 

one way or another I'll get this nut cracked.

[PNAmble]

13 hours ago, crispy_wafer said:

I'm not sure how much of a culprit the mvhr system is

We’ve just done our final air test.  Temporarily taped over the MVHR external ducts outside. Our result was 0.46. So I probably wouldn’t worry too much about that aspect. 

 

 

 

 

[crispy_wafer]

Behold the draft finder mk 1

 

 

[crispy_wafer]

[RobLe]

You can block up an mvhr by wrapping up the filters with clingfilm - I found that a lot easier than blocking off the outdoor vents, as in our case that involves using a ladder on our garage roof!

[G and J]

22 hours ago, RobLe said:

I’ve done this before, and have a set of recommended parts - links below to a suitable fan, power supply, and differential pressure sensor, total under £200.  You can halve that cost by using a car battery charger and no measurement.

https://www.ebay.co.uk/itm/171452099291?itmmeta=01HPJ04NFJ122390GS5BHYCSTA&hash=item27eb576adb:g:AlsAAOSwFLBabz6P&itmprp=enc%3AAQAIAAAA0MHDPIuVE6xMauIT%2B2m3GgQGT8tYsJluxspKLHSwqw2b%2F%2BOcaIly6fBGJylxh3zb5Jt%2BiqjJU5XVvqa3u%2FGMfqCwPjrLEMb5lBzMdLjDfJaGcBD9prP5gR7rYGam3WEHjv5VII7atBOJ1Unhve0fvtuur%2Bo265pYJwGbp2rnHX06VlE%2FewjhoSs4bRG1t%2BVUnBzbF13HZ%2FF3YP7vcD3wY6utJXhe6t2NLy10Vn%2Fn1EUdVjVhKb41RcAUTjvMW8GNMdSgeSgJzKTo1gIgBqDsLTo%3D|tkp%3ABk9SR-jXksC0Yw

 

https://www.aliexpress.com/item/1005003681719599.html?gatewayAdapt=glo2esp

select 15V 20A variant

 

https://www.aliexpress.com/item/1005005320909441.html?spm=a2g0o.order_list.order_list_main.15.44d11802qTJLEi

 

Using those parts, I got the flow versus voltage and pressure relationship below.  Of course, it won’t be super accurate - but what do you expect for £200 of bits?

 

 

So you adjust the voltage to hit the target pressure, but how do you measure the flow rate?

[crispy_wafer]

Theres a post here by @ProDave that gave me something to work with.  As far as measuring pressures and voltage are concerned it's above my head at this point until I do some studying.

 

[RobLe]

Flow rate is super hard - I was lucky enough to have access to a pro blower door, so I compared results between that fan and the pro kit, and made the graph I attached based on it.  The pro kit itself is calibrated, and has two differential pressure measurements - one to give room-external pressure, and the other measures across an orifice at the fan inlet; the data goes into a PC which uses the calibration data to give the flow.

 

If you use the same fan type, you can follow the lines graph I made to give flow at a given voltage and pressure.  

[JohnMo]

11 hours ago, RobLe said:

Flow rate is super hard

You could just use a simple orifice plate. Basically a plate Infront of the fan with a hole in it. An orifice plate uses upstream and downstream pressure to determine the flow rate. You need to make it with a sharp edge so thin metal may be easiest.

 

Use something like the site below to calculate the flow. Use outside air pressure and inside building pressure as the two pressure inputs. So plate has to be outside in relation to the fan, so fan sucking through the orifice.

 

https://toolbox.tlv.com/global/UK/calculator/air-flow-rate-through-orifice.html

[crispy_wafer]

I've got a cavity wall running across my build, and one of these lintels spanning a doorway.

 

I'd completely ignored this but since I've had a look online it appears these are open at both ends into the cavity, albeit with polystyrene wedged into it.  Would it be ok to membrane over and tape up to seal it up do you think?

 

[JohnMo]

21 minutes ago, crispy_wafer said:

I've got a cavity wall running across my build, and one of these lintels spanning a doorway.

I would membrane the lot. Have you sealed the block work? Would that also leak into the cavity? Or is that being plastered later?

[crispy_wafer]

I've been jumping between d&d or wet plaster throughout the build journey, the block work in the loft spaces and areas that will be sealed off once boarded have had a good 2 coats of soudatight lq, so they are definitely better than bare blockwork.

 

I also found the 32mm drain from the mvhr system that I hadn't taped up, it does have a waterless trap on it, but I suspect it wouldn't put up much of a fight during the permeability test, so dealing with that and the 80mm hole I missed will go quite a way to improving the result.