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Testing, testing


vivienz

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Yesterday was air tightness test day and MBC's final day on site getting everything prepped for the final test and then finishing off a few details.  For those not so familiar with this kind of thing, a few details of the process follow.

 

Our house isn't a passive house as it hasn't been designed with that in mind - it was the design first and then build to passive standards, so no accreditation or anything like that.  That said, I wanted a low energy house and hence the choice of the passive system offered by MBC.  Part of this system is that as well as the building and foundation being highly insulated, it also leaks very little air, as this is one of the major sources of heat loss in buildings and houses.  The leakiness of a house is measured in terms of the number of times the volume of air contained by the building passes out of all the various gaps in one hour.  As mentioned on this forum elsewhere, a modern well-built house without any special air tight measures would probably change its volume of air between 3 and 5 times per hour.  The final part of MBC's construction method is to tape over anywhere there is likely to be a gap and make the building as air tight as possible; the target is to have 0.6 or less air changes per hour.

 

One exterior door into the house is chosen as the point of measurement and this is where all the kit goes.  Note that the air tight test is testing the quality of MBC's work and whilst it will highlight gaps elsewhere, it's not MBC's remit to correct leaks caused by others, only themselves.  The point of measurement for my house is the door between the garage and the utility room, where the FD30 rated door was recently installed.  The door is sealed up with a membrane that's supported and held in place by an adjustable frame:

 

1177024322_Doorwayshield.thumb.jpg.d032703a2e2c82c32c54a2911211391f.jpg

 

960988985_shieldandframe.thumb.jpg.fc533b582edfca8f95fa203580ecd784.jpg

 

The hands are those of Steve, of Melin Consultants, who carry out most of MBC's air tests.  This is the frame/shield being put in place in the doorway.  I really did try and get a photo without builder's/air tester's bum, but to no avail.  Those with delicate sensibilities should look away now and skip the next photo.

 

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After the frame, the fan is put into the hole in the shield, drawn tight and any gaps between the frame and door frame are temporarily sealed up.

 

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The rate of air flow into and out of the building is altered by both the speed of the fan and the number of vents that are opened up on the fan.  The building is de-pressurised first, then re-pressurised and the readings taken.  Because of environmental factors such as wind, this is done 10 times to get a data set and the average is taken for the final result.  When this test was done yesterday, it was a windy day with the wind coming from the north east, the direction that the garage door faces.

 

As the test progressed, it became clear that the house is well sealed and so it needed a smaller fan.  The red shield was swapped over and the smaller fan put in place.

 

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The rest of the readings were taken and we got our final reading.  Darren and his MBC crew aced it - with a target of 0.6 ac/h it came in at 0.25.  Brilliant.  Darren is a calm chap under all sorts of pressures but the air test was about the only time I've seen him display (slight) signs of nerves.  He was equally understated in his satisfaction with the result even though it turns out that this is one of the lowest numbers they've had in 7 years.  Well done, Darren and crew.

 

If you're wondering what all that foam is doing on the floor, that's left over from work on the foul wastes over the weekend and foaming them in before putting air tight tape around them to make sure it wasn't detrimental to the air test result.

 

We have a few very minor leaks, mostly gaps between the panels in the windows that have several sections.  No surprise and these are due to be siliconed once we've finished most of the pretty stuff.  There is also a bit of air flow through the keyholes but I've been advised that a good coating of vaseline on the key and in and out of the lock a few times should seal it up well enough.  I daresay that would seal most things.  The gaps were temporarily sealed up with a bit of low tack plastic for the air test, so the result assumes this has been done.

 

All the battens are in now and the downstairs was finished off yesterday, and concrete was put into the remaining recess that had been formed for the lift and slide doors to get a level threshold.

 

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I am, of course, delighted with the air tight result and really pleased for MBC as well, as they have worked really hard and whenever there has been a problem, come up with solutions.  I know that others have had varied experiences but for my own, I have found MBC to be a pleasure to work with right from the start.  At the design stage, David worked his socks off liaising with my architect to get all the details right and to work out how to build the design using their system, and this has been the case with any third parties I've asked them to speak with directly.  The communication from Trish has been great - I've always know what was going to happen and when and been kept informed when timings have had to change.  The guys on the ground have worked like machines; I'm astonished at how hard they work, to be frank, and throughout the whole time I've never heard any rows or arguments.  That's not to say that there haven't been any, but if there have, they didn't take place in front of me.  For me, this has been a really good experience.

 

What next?  There's still plenty to do but the next main contractor is largely doing all of the internal systems, plumbing and wiring (note - I'm no longer giving details of this as I can't recommend due to unfinished work).  The MVHR ducting and manifolds have been worked on but will kick off in earnest on 3rd December once the cellulose has been blown in upstairs.  The cellulose is arriving on Friday 30th, along with Gordon, who will put it into the walls and ceiling.  All 520 bags of it!  Before then, my Ryterna garage door is due to be installed next week so I'll report back on that.  That's being supplied and installed by Joe from Dorset Garage Doors Ltd, just up the road from me in Lydlinch.

 

There's a lot of work to be done outside, too, but I'll be thinking through that today and get my plan of action together.  Whatever else happens, some gentle heat will be put into the slab this week, using a couple of Willis heaters.  It's getting pretty chilly on site now and it will be nice to get the house drying out properly and check that side of things is working properly.

 

A good week and, hopefully, more to come.

air test gadgets.jpg

fan openings.jpg

sealing a few gaps.jpg

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Great news and it is good to hear you are really pleased with your trades people. Very interesting to read as well.

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Nice, we used to have a ACH leaderboard on the go somewhere - I think you're at the top of the list! (we got 0.56 I think - not bad for 400m2 with a basement)

 

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I think there should be a Top Gear style leader board. It'd give something for others to aspire to.

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Brilliant result, IIRC we were 0.43, so you're way better!

 

As encouragement, I can say that it was snowing today, then cold, sleety, rain, and we're sat in our beautifully warm and cosy MBC home, walking around in bare feet and just enjoying the superb level of comfort that a super-insulated, airtight, house gives.

 

For the keyholes, if they are deep ones, then get some motorcycle chain lube.  It comes in an aerosol with a thin pipe on the nozzle, like WD40.  Shake the can really, really well, then spray the chain grease as deeply into the keyhole as you can get.  It will set nearly solid in the middle, as it's designed to be really thick so that it doesn't fling off motorcycle chains, and will last years as an air block in the centre of the keyhole.  If you get the white stuff then a bit of spillage into the key mechanism doesn't make too much of a mess.

 

I tried a silicon grease spray initially, but found it tended to melt out in hot weather.  The motorcycle chain grease stays solid, even in fairly hot weather.

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18 minutes ago, Onoff said:

And there's me destined to die in fuel poverty being eaten by cats!

Lounge just now:

:)

 

Lounge just now (outside wall):

 

image.thumb.jpeg.924b1a4bd8c3dd07fba66880becc2bd4.jpeg

 

No cats (yet...), thank goodness...

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6 minutes ago, JSHarris said:

 

Lounge just now (outside wall):

 

image.thumb.jpeg.924b1a4bd8c3dd07fba66880becc2bd4.jpeg

 

No cats (yet...), thank goodness...

 

Me neither but they can get in through the big holes where the heat's getting out! :)

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13 minutes ago, Onoff said:

 

Me neither but they can get in through the big holes where the heat's getting out! :)

 

 Cats ? or rats ?? ?

 

Great result @vivienz

 

 

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What happens now you achieved this enviable reading. Do you address the minor leaks and test again. Or do you just accept a brilliant result that can likely only get better?

 

How low can it go?

 

We could run a book on the result! :)

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1 hour ago, Onoff said:

What happens now you achieved this enviable reading. Do you address the minor leaks and test again. Or do you just accept a brilliant result that can likely only get better?

 

How low can it go?

 

We could run a book on the result! :)

 

7 hours ago, jack said:

Awesome result, and that with some minor leaks still to be addressed! 

Considering this is without the cellulose blown in yet, it’s going to get a fair bit better me thinks. 

+1 to Darren’s tenacity, top guys doing top work, and all ( annoyingly ) in their stride. ?

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It's a law of diminishing returns.  In a windy location, getting better than 0.6 ACH might give  a small benefit, but in most locations I doubt that their would be any noticeable difference.

 

One factor that starts to dominate is how often you open the outside doors. We had our front door open a fair bit this morning, whilst shifting furniture, and that dropped the temperature by a couple of degrees.  Only took around 20 minutes or so to warm back up, though, as all the heat stored in the slab quickly brought the house back up to temperature.

 

 

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I wonder what my bathroom would test at when finished... :ph34r:

 

A few too many "openings" at the mo; conduit drops open to loft, wc pan "odour" take off to loft, wall drain with empty trap...

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9 minutes ago, JSHarris said:

It's a law of diminishing returns.  In a windy location, getting better than 0.6 ACH might give  a small benefit, but in most locations I doubt that their would be any noticeable difference.

 

One factor that starts to dominate is how often you open the outside doors. We had our front door open a fair bit this morning, whilst shifting furniture, and that dropped the temperature by a couple of degrees.  Only took around 20 minutes or so to warm back up, though, as all the heat stored in the slab quickly brought the house back up to temperature.

 

 

 

So is "m3/m2.h" the same as "ac/h"?

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1 minute ago, Onoff said:

 

So is "m3/m2.h" the same as "ac/h"?

 

No,, unfortunately not.  The whole world (except the UK) uses ACH.  Why we have to relate airtightness to floor area is beyond me.  Logically, the air change rate should relate to volume, not floor area, as the latter takes no account of differing ceiling heights, and lost heat relates to the volume ratio, to a significant extent.

 

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4 minutes ago, JSHarris said:

 

No,, unfortunately not.  The whole world (except the UK) uses ACH.  Why we have to relate airtightness to floor area is beyond me.  Logically, the air change rate should relate to volume, not floor area, as the latter takes no account of differing ceiling heights, and lost heat relates to the volume ratio, to a significant extent.

 

 

So how good is 0.47m3/m2.h in relation to the "0.25" figure quoted here?

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Depends on the volume. 

 

For example, our house has 2.4m ceilings in the ground floor rooms, but the hall is 2m wide and goes up to around 6.5m at the apex, and the bedrooms and bathrooms have ceilings that are vaulted and go up to about 4m or so.  The consequence of this is that our 0.43 ACH figure equates to 1.22 m³/m²/h, which is a (perhaps extreme) example as to how misleading the UK BR measurement can seem way out of kilter with the generally accepted ACH measure used virtually everywhere else in the world.

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42 minutes ago, JSHarris said:

Why we have to relate airtightness to floor area is beyond me.

 

I'm pretty sure it's total external area, not just floor area, including walls and roof so it's a direct measurement of the quality of fabric.

 

From: https://www.stromatech.com/building-performance-testing/air-tightness-testing/air-tightness-compliance/

Quote

 

What is “Air Tightness”?

Air tightness (also called air leakage or air permeability) is measured in m3 of air, per m2 of envelope, per hour, at 50 Pascals differential pressure between the inside and outside of the building [m3/(m2.hr)@50Pa].

The “envelope” is the shell of the building that contains the conditioned air. In most cases, this would comprise the ground floor slab, the perimeter walls and the underside of the roof. If the roof-void is naturally ventilated, the top floor ceiling becomes the top part of the envelope.

 

 

It's a pain to have two systems in use. The rest of the world (including Passivhaus) uses air changes/hour (often written ACH or AC/h). The m³/m²/h and AC/h numbers are often similar which makes things even more confusing but there's not a direct conversion between them as the ratio depends on the size and shape of the house.

 

For a given fabric leakage rate (m³/m²/h) and a given shape a larger house will have a lower AC/h rate than a smaller one. Obviously, houses aren't scaled up without changing their shape but this is one of a number of reasons why Passivhaus tends to be easier with large houses so encourages building bigger. It's one of the reasons I'm not 100% sold on Passivhaus in detail as opposed to in principle.

Edited by Ed Davies
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Mine came in at 0.58 so although within the MBC contracted limit of 6 and I’m fine with that it seems poor by comparison to others here. I suspect that the finished house is nowhere near 0.58 because it was very air (and water)  leaky for the test with windows not fitted properly etc (everything was just temp taped over by the air testers and I was told by the testers it needed to be properly sorted) the issues were never properly resolved afterwards and I have seriously cold areas around the window/wall junctions. The areas around the tilt and turn windows in the rendered walls seem worse than the sliders on the clad walls. I have areas in some rooms that feel colder to sit in if nearer windows/walls and I have altered positions of furniture to take account of these cold spots.

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22 minutes ago, lizzie said:

... I’m fine with that it seems poor by comparison to others here. 

 

To be fair, 0.58 is a stunning result by any other measure - something like 10 times better than building regs requires. We managed 0.56, so only slightly better than you. The big slider in our kitchen seems to be the worst single contributor, and unfortunately it isn't adjustable.

 

You may be able to get some improvements by adjusting the windows so they pull in a little more tightly. We've done that as best we can, but a couple of windows just don't seem to be adjustable far enough to get a proper seal. We get definite air (and hence sound) leaks in those rooms. 

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