Bad Airtightness Test Result

[Oz07]

What are you @tonyshouse

[tonyshouse]

42 all in 

[AliG]

If I exclude the area of the pool room as the pool heater also heats that room, I am getting around 40,000 kWh a year to heat 800 sq metres, or 50kWh/m/yr. This does indeed suggest that the airtightness is not having much of an impact.

 

Having rooted around a bit, my suspicion is that in lots of places the builders have stuffed gaps with rock wool, which is enough to stop normal draughts/wind, but not for the air tightness test.

 

So I opened up the area that I had found was an issue after we moved in and asked the builders to fix. Basically they had filled the partition with rock wool and put a layer of plasterboard on it, but not sealed the actual area where the air gets in. The problem is that this area connects to the area where the MVHR is above the ceiling on the ground floor and thus impacts most of the house.

 

I took some pictures but its s had to see.

 

f you look at the picture from outside, we have an area where a sloped and flat roof meet.

 

If you look at that area from inside the hall you see a cross. There is a vertical steel in there that you can see from the pictures taken inside the offending area.

 

So if you look at the pictures where you can see the airtightness membrane, that is on the end of the sloped roof, but the area of render board is not airtight and is open behind the plasterboard cross own the hall which connects to all the downstairs ceiling and the MVHR run to the WC. Effectively if cold air gets in here it can get all over the house and the unsealed area is large.

 

Now how do I seal it? 'the gap between the end of the roof and the stud work is only around 100mm wide, effectively this is where the builders had sealed it, they foamed in some plasterboard (They also put some odd bit of plasterboard inside the studwork when they ran out of insulation!), but all the air above this could still get into the walls and ceilings. The only thif I can think of is firing spray foam up to the top of the gap all around the steel to seal it in. I don't like filling a massive void with foam, but there is not way to physically get up into the space and seal it up.

 

 

 

 

 

 

Edited December 6, 2020 by AliG

[AliG]

I have been through all the pics I have of the build. The problem area is marked up between the end of the roof and the steel. It just seems there was never any thought given to the point where they meet.

 

Now I have these it looks like the vertical steel I can see in the space has Porotherm blocks on the far side of it so I think I can safely seal it to them with foam.

 

The issue then is sealing the top area. There is a point where I managed to get a picture showing some light and there were leaves in there so it is def open to the outside.

 

 

 

Edited December 6, 2020 by AliG

[TonyT]

You can extend expanding foam guns with a length of clear flexible pipe, makes it easier to get into difficult spaces.

 

once i have more Christmas decorations out the loft, I will be doing the same draught remedial works too!

[tonyshouse]

I have a 1m long foam gun with a dog leg at the end .   But seems to me bit like a colander 

[AliG]

I have a rough list of things that I want to do.

 

My suspicion is that they will have negligible impact on my gas bills, but a big impact on the airtightness test. They might also help with noise transmission which I am always keen to cut down.

 

I have a load of foam, sealant etc ordered up.

 

I might be doing the 12 days of airtightness. I am sure it is things that other people would have done as they went along whilst building. I suspect many of the things I am looking at could be applied to any house no matter the age.

 

Whilst that area in the roof was def a big part of the bad test result, the air was blowing through very fast even though in normal circumstances I hadn't noticed any draughts, the other thing I think considerably impacts the test result is various cable and pipe runs that end in the loft and are not sealed at the top, so I will be getting them sorted out where I can.

 

There are two places where I suspect to properly fix things I would have to cut a hole in the ceiling which I would rather not do, but lets see how it goes.

Edited December 7, 2020 by AliG

[AliG]

I made a start after work. Took me two hours to seal around 25 linear metres of skirting board to the wooden floor below it.

 

If I seal it all up I think there is 200m to do ?

 

I will need to order more caulk as I have already used 1.5 tubes.

[LA3222]

20 minutes ago, AliG said:

I made a start after work. Took me two hours to seal around 25 linear metres of skirting board to the wooden floor below it.

 

If I seal it all up I think there is 200m to do ?

 

I will need to order more caulk as I have already used 1.5 tubes.

Good times? Just remember, as painful as all this seems now in a years time it will be a distant hazy memory long forgotton?

 

I dont know what the U values are for your build but the sheer size should surely mean that the internal volume is massive and ventilation heat losses will dominate all else.  Everything you do to knock that ACH rate down should surely make a material impact on heat loads?

Edited December 7, 2020 by LA3222

[tonyshouse]

Sealing skirting to the floor in many cases is like closing the door after the horse has bolted, definitely upstairs it is

[Oz07]

His horse has bolted!

[AliG]

Oh I know skirting is not the most important job, I just don't have the stuff to do the other jobs.

 

There was an absolute gale blowing through the space in the eaves during the test and then there was a hole from the eaves into the ceiling of the ground floor where some cables went through. Sealing all this up will make a big difference. Funny thing is I had identified this area and thought it was fixed.

 

I am not convinced that the test result is representative of the real world other than on a very windy day. Most of the places where you could feel cold air coming through I have never felt any cold air at all nor have I seen anything when using the IR camera on a cold and windy day.

 

I will be up in the loft sealing the top of the soil stacks once my tape, foam etc come. This is the other job that will make a big difference.

 

I suspect that I can get a considerably better result in the air tightness test. Whether it saves more than 5 or 10% off my heating bill I would be very doubtful.  However, I don't like things not being done as well as at least reasonably possible. Clearly doing this when the shell went up would have been ideal but I cannot go back and do anything about that.

[daiking]

12 hours ago, AliG said:

I made a start after work. Took me two hours to seal around 25 linear metres of skirting board to the wooden floor below it.

 

If I seal it all up I think there is 200m to do ?

 

I will need to order more caulk as I have already used 1.5 tubes.

Keep going, you'll get there.

 

I had to crawl into the floor void last week to pull a cable for outside Xmas lights. Which was a clear reminder of why its taken me 5 years so far not to insulate the suspended floor yet. 

[tonyshouse]

You say , “I am not convinced that the test result is representative of the real world other than on a very windy day. Most of the places where you could feel cold air coming through I have never felt any cold air at all nor have I seen anything when using the IR camera on a cold and windy day.” 

 

yes but it could also be that hot air is escaping by chimney effects warming or keeping stuff warm on its way out 

[AliG]

That’s a good point.

 

I have spent the last hour up in the loft investigating where there are holes that I can seal up.

 

Around the stacks and other pipes that come up from the ground floor once I pulled up the rock wool the bottom layer of it was warm.

 

At least this is a relatively easy fix. Someone had made a feeble effort to seal one of them

 

 

[tonyshouse]

Only another 10 million to now then ?

Here is one I did earlier 

https://readinguk.org/draughtbusters/basic-techniques/loft-and-first-floor-ceilings/ And scroll down 

 

 

[AliG]

10 hours ago, tonyshouse said:

 

Only another 10 million to now then

 

I thought I should clarify that the feeble effort at foaming up the hole was not me.

 

Thanks for the website. The whole ceiling was done before the partition walls so the only thing to seal up is the pipe and cable penetrations of which there are probably around 20.  It would have been a lot easier before the insulation was down.

 

When the plans were drawn up this was shown as a warm loft. I did consider was it my fault for changing to a cold loft as it was a lot cheaper.

 

I certainly think it shows that you are a lot less likely to have issues with a warm loft. However due to the very complicated roof shape of the house I don’t think the full loft could have been easily made airtight and it might have been even worse in my case. I would have had an even larger heated space with lots of holes. But it is certainly something to consider.

[ProDave]

Reading this thread and all the sealing of holes from the house to the loft just confirms my belief that the way to get a truly good eficcient house now is a warm roof, so all the loft space (if any) is within the warm sealed envelope of the house.  It is only services in and out of the building that have to be detailed and sealed.

[AliG]

I think that is true @ProDave The only issue that I have is the loft has numerous corners, dormers, changes of height etc and I am not convinced that the the builders would have actually managed to seal it all up either way (as you might see from their efforts to seal around the SVP)

 

We'll know once I have sealed everything up and we redo the test. The architect is getting the builders back in as he confirmed that there should be a cavity closer on the cavities that are open to the roof. There is roughly 10m of this, I am not sure if it impacted the test result.

Edited December 9, 2020 by AliG

[AliG]

Continuing to work on sealing things up.

 

When the test was done the ducts for the pool dehumidifier had insulation filling the gap as they went through the wall but it was not taped up so I did that.

 

I discovered that one of the ducts was not sealed up on the far side as to do this required me climbing on top of the ducting, which thankfully easily took my weight, and lying in my back up in the air to tape up the space above me.

 

My hope is that 5 or 6 areas like this we have identified as quite big gaps are the main culprits in the low airtightness score.

 

I did also discover another thing. There is an area of about 15 sq metres of wall that seems like an interior wall but is above the loft insulation so should have been insulated. It is currently landlocked in the join of the T in the roof so I think just no one noticed it.

 

I have attached an IR picture where you can see the area of wall that is a couple of degrees cooler. 
 

IMO having started this work. Tape is the way to go to seal stuff up. Foam is nasty stuff that works well if you have a narrow gap but often just falls out of holes and goes everywhere.

 

 

Edited December 15, 2020 by AliG

[john0wingnut]

On 15/12/2020 at 11:13, AliG said:

Continuing to work on sealing things up.

 

When the test was done the ducts for the pool dehumidifier had insulation filling the gap as they went through the wall but it was not taped up so I did that.

 

I discovered that one of the ducts was not sealed up on the far side as to do this required me climbing on top of the ducting, which thankfully easily took my weight, and lying in my back up in the air to tape up the space above me.

 

My hope is that 5 or 6 areas like this we have identified as quite big gaps are the main culprits in the low airtightness score.

 

I did also discover another thing. There is an area of about 15 sq metres of wall that seems like an interior wall but is above the loft insulation so should have been insulated. It is currently landlocked in the join of the T in the roof so I think just no one noticed it.

 

I have attached an IR picture where you can see the area of wall that is a couple of degrees cooler. 
 

IMO having started this work. Tape is the way to go to seal stuff up. Foam is nasty stuff that works well if you have a narrow gap but often just falls out of holes and goes everywhere.

 

 

Is that one of the Flir Cams for iPhone / android?

[AliG]

49 minutes ago, john0wingnut said:

Is that one of the Flir Cams for iPhone / android?

Yes, it is absolutely fantastic for checking things over. I managed to get a refurb one so got a reasonably good deal on it. It is very sensitive and you can see quite small temperature changes.

[AliG]

Working ob this now that I am on holiday!

 

I have a laundry room and small kitchen upstairs. Both of them have pipes through the wall to a small eaves space. I have taped these up.

 

I thought I was being smart having the rooms fully tiled before the cabinets were fitted as this would seal everything up. But I forget the ingenuity of builders to avoid any small amount fo work if they possibly can. So although the rooms were totally tiled, I never told them to also grout them. Therefore they waited until the units were installed and then just grouted the area you could see leaving a nice gap along the edges where the plasterboard meets the floor. Depending on the access I have either taped or foamed these gaps. It would have taken minutes extra to grout the entire floor versus hours for me to clear everything out of the rooms, remove plinths, vacuum under cabinets, stretch into corners etc.

 

So if I was giving any tips, don't just tile before fitting skirting, kitchen cabinets etc, also make sure it is totally grouted, not just the areas that can be seen.

 

I have the same job still to do in the main kitchen. I can feel a draught from under the island, I have only noticed it recently with the temperature close to zero. I think there is a conduit from the island to one of the soil pipes as the hot and cold water run in the space. Shouldn't be too hard to seal.

 

Tape is much much better than foam, the only issue being that you are limited to the length of your arms. Not only is spray foam nasty messy stuff but in this kind of situation you are not guaranteed it expands into the gap, it can easily expand away from them.

Edited December 28, 2020 by AliG

[Gav_P]

23 minutes ago, AliG said:

Therefore they waited until the units were installed and then just grouted the area you could see leaving a nice gap along the edges where the plasterboard meets the floor.

That’s shocking cowboy behaviour. What’s the point in tiling and not grouting?!? Ffs makes me really angry and it’s nothing to do with me!... I’m off to get a stiff drink! 

[AliG]

6 minutes ago, Gav_P said:

That’s shocking cowboy behaviour. What’s the point in tiling and not grouting?!? Ffs makes me really angry and it’s nothing to do with me!... I’m off to get a stiff drink! 

 

Every house I have had previously they only laid the kitchen floor up to the feet of the kitchen units, I thought I was being smart asking for the whole floor to be done.