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A raging convection flow and a cold nose...


curlewhouse

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It has been a cold few weeks here at Todcroft, with -13c at one point, which saw us flee from the caravan when all water, toilet and even the LPG froze and no longer worked. So we set up in the house even though we only have temporary polythene windows.

 

But this bad weather (to be expected of course) combined with lack of windows and just (triple glazed :D) polythene in place of glass, has meant running fan heaters pretty much 24/7 to even keep slightly warm, though that's a misnomer as your never actually "warm" just ever so slightly less cold....... we just got our resulting £500 electricity bill!

 

Even with three 2kW fans running, you need thermal underwear, a couple of fleece jumpers and often a warm hat on! To be honest, I've felt quite bad for my wife at times, and there have been tears when sometimes it seems as if there is no end in sight, exacerbated by the attitude of the building warranty people just throwing barrier after barrier in our way to stop us making progress. I work out doors, and grew up in the Northumberland countryside, so am pretty hardened to the cold, but even I have found it very cold and pretty miserable.  But, even without us mentioning how bad it has been, we've been offered spare bedrooms by several friends and neighbours, and one work colleague even offered us their entire house over Christmas as they would be away! There really are some lovely people out there.

 

We invested in an electric blanket, which is great - though now you don't want to get out of bed into the cold :D.  Your body is warm, but your head and nose is frozen!

 

Anyway one of the many issues our BCO/Warranty Inspector has with SIPs is that he is convinced they shrink massively. One of the numerous enquiries he made me do with the different companies for him was to find out the shrinkage (yes, I know, I too pointed out to him that OSB has, as the name would suggest "oriented" strands, which by going in different directions, largely mitigate against this when compared to standard timber) from Kingspan - as around this time I'd had enough and told him that as a BCO he was more likely to get a comprehensive answer than I was when he kept making me go back time after time to the suppliers, challenging their methods and suitability of the materials (even the BBA markings on each SIPs panel were not enough for him to believe them to be an "approved" building material in his view!) . So he contacted Kingspan who gave him a figure (I forget now, but it was absolutely tiny). So he spoke to our mason and made him leave a whopping great gap  around the entire house between the stonework and the fascia/soffit  to allow for the SIPs shrinking.  Now on one level I get his thinking, that if the soffit was hard against the stone, then if the SIPs did shrink to any appreciable degree, it would presumably force the soffit out of place or crack it.  But this massive gap all the way around makes for fantastic and constant convection from the air bricks at the bottom, and none of us are convinced the shrinkage will be anything like he fears, if it happens at all.  Yes, the cavity definitely needs to be ventilated to stay dry, but this big a gap all round will set up a constant and quite massive convective flow in my mind - and we are trying to build a low energy house!  OK, so the cold air will be rising against the outer OSB, behind which is all the SIPS insulation, but it's still going to be a constant and high flow situation (I used some smoke on the one still day we've had and there is a clear constant convection going on, even with the tiny amount of heat we have inside right now) drawing heat off.

 

So my thought is to use foam or similar compressive material to close most of this gap up. Though I think I'll insert something like wire mesh in places to allow some air flow still for obvious reasons, but I think it surely doesn't need to be a raging flow 24/7 around the entire perimeter. The trouble is, if I were to ask the warranty guy what material he'd recommend, he'll either insist we allow the place to lose heat and do nothing, leaving this gap all around, or he'll make me contact the SIPs manufacturer/foam manufacturer/builder et al to "ask if its a suitable material to use with SIPs" (as that's the answer I get to everything from him if I ask - making me seem a pest as I keep having to go back to these companies and pass on his often silly questions). 

 

On a more positive note, we now have some movement on the windows. Being unable to afford the likes of Internorm or their ilk, we've had to look at the usual mass double glazing suppliers.  In the end we chose one of the 3 big national firms, and all seemed OK. They took our deposit, the salesman wasn't pushy, and all seemed fine.  Then no one came to measure up. Eventually, after me chasing them, someone came 3 weeks later to measure up - and promptly refused!  The stonework is all done with the exception of the sides and tops of the first floor windows. But that's OK as the inner is SIPS, where the windows will be mounted of course, and so the sizes are already set.  So he said he'd get the ground floor ones going for now so at least we'd have those in. Then when he got back to the office changed his mind and they simply refused to continue until the whole thing was complete, and only then would he come back and measure, and even then, we'd have to wait "6 to 8" weeks for them to install. So this takes us into possibly April with no windows - and them holding our deposit meantime!  I pointed out that how come I myself had managed to fit a far more complicated (cabrio type) window on the first floor already but they were saying they couldn't even start making them, least of all fit them?) So we were stuck, we'd signed the contract, they had our money and were going to do nothing more for weeks despite us literally freezing in here.  Then there was a break.

 

We got a letter from them saying as a new build our house was "unsuitable for their product" - now since they'd already strung us along well over a month, I rang and challenged this asking why waste so much of our time. Turns out it referred only to the French doors and they were sending us a new contract for only the windows. But, they'd sent us a letter nullifying the whole contract.  Meantime, on visiting a retired builder friends house and admiring his windows I discovered they were made and fitted by a local firm, and I was surprised when he told me the very reasonable price given the clear quality.  So I got them to come out, and their attitude could not be more different. So I used the other firms (Anglian) cancellation letter, wrote to them telling them we accepted thier cancelation of the contract (as I'd feared they'd try and keep our deposit if we cancelled) and please refund our deposit, which they have agreed to.

 

So for less money  we are getting a better U value, triple glazing (yes, for less than Anglian were charging us for double glazing) and they are fitting the French doors this Monday and measuring up for the rest on Wednesday, and on realising how cold we are  promised us that it will be 4 weeks at the very latest! Plus I've seen the quality and it is excellent. (this is actually my friends house on their web site   https://hawthornswindows.co.uk/portfolio/view/  )   We can't wait to be warm! :D

 

 

 

 

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21 Comments


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You need a fibre cavity sock to close that off - they are a standard product which you can just leave a few small “gaps” in to vent but that is all you want. 

 

And well done on the windows ..! 

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Speaking as a fellow caravan dweller in this cold winter, I would say the best thing we did was fit a wood burning stove in it.  It has been running continuously all November and January so far.  Having enough free firewood obviously helps that situation and we put coal on it overnight so it stays in for the night (usually)

 

That on it's own mostly keeps the caravan warm enough and we use electric convector heaters in the bedrooms overnight. Electricity bill running at about £80 per month.  LPG should not freeze. You are using Propane aren't you, not Butane (which will not off gas much below 0)

 

Upon installing the 'van I added more insulation to the pipes, insulated under the floor and panelled in the gap between the 'van and the ground. Nothing has frozen in this cold Highland winter, not even when we went away over the Xmas / new year break and left it to it's own.

 

Re Windows, have you tried Rationell?  For me they were the cheapest of the quality window suppliers and I am very happy with them.

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Yup, easy enough to bust that down to trickle vented, and buy your friend a bottle of their favourite plonk....excellent result. 

If it helps you a little, id happily freeze my arse off for the duration if I could build my own home, I genuinely would. Look to the future, and remember this isn't forever. ;)

 

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Yes it was on butane when we got the caravan,  but I changed over to propane once the temperature dropped. As for insulating the outside pipes etc.I really did not want to spend time working on the caravan as I've got so much ahead of me in the house to do. I'd had to replace a tap, loo pump and sort the hot water system out soon after getting it and really have no spare time or spare cash to spend either on the caravan, hence abandoning it and moving into the house. Next move will be my wife giving it (the caravan) a good clean up in the spring and we'll sell it on. Unfortunately we'd also had to move it from a sheltered position  on hard standing on the site (when more stone and sand was delivered) to a muddy hole and broadside on to the prevailing wind, so it was far from optimal. It has served it's purpose though.

Edited by curlewhouse
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17 minutes ago, curlewhouse said:

"Next move will be my wife giving it (the caravan) a good

......dousing with kerosene and ?" I thought that was going to read :D

  • Like 1
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22 hours ago, Nickfromwales said:

......dousing with kerosene and ?" I thought that was going to read :D

... actually, she HAS suggested that! :D.

 

When we first got it she says "oh, once the house is built we could keep it and maybe have the odd weekend away with it" - 2 weeks later she's fantasising ways to blow it up! I think it's safe to say we won't be keeping it :D 

  • Like 1
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Good point PeterW, and there are cavity socks all over, round all the openings etc. Unfortunately the gap is too small to fit anything much in now.  I guess something more compressable than the fascia & soffit board will be the thing (I suppose I could stuff it with rockwool and maybe close the front of the rockwool off to keep it dry with silicone, all tucked well back so it's not visible so doesn't look odd.

 

Our mason also pointed out (quite rightly) that we'd have the worlds supply of wasps nests, bats etc in our walls with that gap left as it is.   

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Have a look at compriband expanding tape.

 

Now is the perfect time to install it, while it is cold (keep the roll somewhere cold until you need to use it)

 

In this cold weather it takes a long time to expand, so plenty of time to unroll it and slide it into the gap then it will gradually expand to fill the gap.

  • Like 2
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1 hour ago, curlewhouse said:

Good point PeterW, and there are cavity socks all over, round all the openings etc. Unfortunately the gap is too small to fit anything much in now.  I guess something more compressable than the fascia & soffit board will be the thing (I suppose I could stuff it with rockwool and maybe close the front of the rockwool off to keep it dry with silicone, all tucked well back so it's not visible so doesn't look odd.

 

Our mason also pointed out (quite rightly) that we'd have the worlds supply of wasps nests, bats etc in our walls with that gap left as it is.   

 

How big is the gap...?? And how many airbricks are there..?

 

Not condoning this behaviour at all, but I'm with your mason and tbh as soon as its signed off I would be stuffing all but 2 of the airbricks with expanding foam, and the others would get stainless steel wool in them to keep the wasps out !

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Airbricks are every 1800mm as per architect plans/regs, but its more that massive all-round gap (200-300mm all along on the front & back elevations of the house) that concerned me really. On their own the air bricks are not an issue and it was that massive all round gap ensuring far more than the gentle air movement required to stop damp/moisture build up which meant we'd be wicking off heat constantly, albeit on the far side of the insulation, which concerned me (not to mention all the beasties which would be living in the cavity of course) . I don't know anyone else whose doing timber frame or sips with a stone/brick/block outer to know if this big and all round a gap is normal or if its yet another of my BCO/Warranty Inspectors own special rules.    

Edited by curlewhouse
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I’m lost ... got a picture ..??! 

 

Soffit vents need to be 10-15mm at most, and that’s continuous for the roof usually. 

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I haven't got any airbricks in my stonework.

I am worried now that I should have.

I didn't see any on @TerryE stone work.

I have a closed panel timber frame.

I have 1.5 m of stonework on the rear, either side of the 6m of glazing, & 1m & 5m on the front, to the underside of the roof overhangs. Single Storey.

50mm cavity.

 

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Moira, don't worry, in fact your post made me go back and look and of course you are correct! My ventilators actually only ventilate the underfloor cavity and only appear to be in the walls because they have telescopic extensions ... as I should have remembered since I fitted them  Image result for Doh .

 

 

 

 Image result for telescopic ventilator

 

 

So the current high level of air flow coming out of the top gap is coming in via the cavity openings where I have not yet fitted all the cavity closers. After that the only real in-flow should be via the weep vents at the sides of the ventilators, sills etc.  So thinking more about it, the incoming air flow will be greatly reduced, but I still need to block a lot of that top off to keep it in check and keep out all the creatures that would no doubt end up accessing our cavity via it. Compriband does seem an ideal solution, with a wire mesh gap at one or two places to allow some flow to ensure it doesn't get damp.  

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Phew!

Thank you.

I too have telescopic vents to ventilate under the beam & block.

I have a problem with gaps around one window & the patio doors where the stonework doesn't quite close the cavity.

Trying to figure out a solution at the moment.

 

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On 28/01/2018 at 14:47, ProDave said:

Have a look at compriband expanding tape.

 

Now is the perfect time to install it, while it is cold (keep the roll somewhere cold until you need to use it)

 

In this cold weather it takes a long time to expand, so plenty of time to unroll it and slide it into the gap then it will gradually 8expand to fill the gap.

I took your advice and bought a roll of compriband to try. I'm well impressed and have ordered more rolls. As the stone is random sized,  the gap varies considerably, so the ability to buy different expansion sizes makes it  the perfect solution. The soffits themselves are of the ventilated variety though I'll still leave some air gaps of course, but with mesh to stop insects. Where we are, there's a good 10+ miles  clear down the valley between our house to the moors opposite, so we get a fair old blast from the prevailing wind off the moors so I'm quite happy we'll still get ample ventilation in the cavity.

Edited by curlewhouse
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This thread has made me think about my build.

I do not have an architect on board so am learning as I go along.

I have a small 10 -12mm gap from the top of my stonework to the underside of the cedar clad overhangs.

I was going to have this pointed up to close the gap.

I have a closed panel timber frame with a 50mm cavity & ironstone cladding.

This is only for relatively small areas on the front & rear elevations.

There are weep vents at the base of the stonework.

Your thread makes me think I will need some air vents at the top.

The gap is so small I may have a problem finding something.

Would manthorpe weep vents spaced & placed horizontally be suitable with the lime mortar pointing in between?

Any ideas gratefully received.

The cedar cladding is going to continue either side of the glazed front door & sidelights on the right of the photo.DSC01422.JPG.aca8dd537b6722efffc479f87bd2a7ad.JPG

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You need to start by asking the question as to where will moisture get in from ..??

 

Continually venting cavities has been proven to be inaccurate - just look at how we went from 9” solid to a pair of 4” “cavity” walls  to stop damp and now we pump them full of insulation ..!

 

You may need a small vent every so often but I would want that filled to stop wasps etc getting into the gaps 

 

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Thanks Peter,

There shouldn't be any moisture getting in really.

I was thinking of something like the weep vent below fitted horizontely, one at the top of each area of stonework with the rest of the gap filled with lime mortar.

This would make one vent for about a meter of stonework.104_1_720x550.jpg

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