willbish

Yeh good point, it doesn't add a great deal if paying ~£40m2 for Icynene

Thanks Peter, and did you butt the joints up tight or follow the MI's and keep a 3mm expansion gap. Im assuming you didn't bother to tape the joints. Yes I think the thickness is important, in this demo example spray foam has been used to prove how well it performs at creating an airtight layer, coming in at 1.246m3/h.m2. The foam is moderately thick, they've used decent backing/sarking throughout and the foam hasn't been trimmed in places which seems to help by not disturbing the joints between foam and rafter. In a recent email Icynene said to me, "we regularly achieve figures better that 1.5m3/hr/m2". If I convert this to AC/H for my whole house the result is understandably poor. Therefore I need to balance the relatively poor airtightness of the roof compared with the good airtightness of the ICF (hoping for something less 0.5m3/h.m2 here, excluding openings) Its hard to quantify how much effect the following have in creating an airtight layer with spray foam: Thickness of foam Whether its trimmed back Type of sarking or backing material Brand of foam I'm finding it all a bit ambiguous and wondering whether taking the membrane route may be a safer option for a guaranteed <0.6AC/H

Hi Peter, was the OSB you used the T&G variety with joints glued or was a butt joint sufficient? I'd also like to do away with an airtightness membrane and go for Icynene but cant afford to do both! Therefore I need to ensure a solid airtight score from the Icynene and sarking.

It's not a belief it's a need. I am rebuilding on the footprint of an existing cottage. Think low ceilings and low ridge height. Ridge height cannot be increased due to local architecture. Upstairs rooms cannot be pushed further into the attic space due to the requirement to maintain volume of attic for bat roost. The distances the joists need to span mean that PS8 were adequate, why use a deeper joist if you don't have to? Architect even specified PS8. It's no bother I'll just use Easi joist, 195mm depth, which have very similar span tables. I'll even gain 7mm but crucially will be able to fit 110mm soil pipe through the web.

It's ICF. What I'm struggling to understand is, why design a joist that can't fit a soil pipe through when the unique selling point of posi joists is that they are great for services!

Just noticed on posi joist spec that the space between the flanges on their slimmest joist (202mm) is 108mm, therefore not big enough for a 110mm soil pipe?!? Easi joist on the other hand, slimmest joist 195mm and 125mm between flanges. I have been through several design amendments with the posi joist dealer but seems that was all in vain.

@scottishjohn I like the idea of not having to carry around lots of different length cable ties, instead simply carrying a gun and reel.

Thanks @newhome Yes it is! Me neither. So many times I have had to use cable ties which are the wrong length. Either joining two or more together or wasting long ones and cutting off the excess. Not any more!

Has anyone seen anything similar available in the UK?

Isoquick say that pipe and ducts passing through the system should do so vertically. Page 9 Isoquick Introductory leaflet and technical notes.pdf

And I would guess you service room is always going to be slightly warmer than the rest of the house, which would also help to highlight any issue.

Thanks gents, From the installations Ive seen it looks best practice to insulate incoming ducts regardless of whether they are inside the thermal envelope or not. That's reassuring ? I will most likely be using the 75mm semi rigid ducts too. Out of interest how do you know you don't have a slight condensation issue? Were all your systems up & running, before the ceilings were covered up?

Ive recently been trying to chose a MVHR unit and have approached a few companies who design & supply. As I will be cooling my slab with ASHP its just a little extra work to add a duct cooler to the Intake. I've been advised there may be condensation issues as cooling the intake air will increase the relative humidity. @JSHarris when you say Is this regarding your air to air MVHR or your additional duct cooler? Has anyone else installed a duct cooler and what is necessary/advised to take measures to prevent condensation? Many thanks

That's reassuring and much appreciated, thank you @A_L

As part of a quote for spray foam insulation I got some condensation analysis done. Should I take issue with the following from attached analysis -Outside temp 5*, wouldn't 0 or -5 be better to show larger gradient -Similarly inside temp 15*, as above, also plainly not accurate -Missing layer, I will be using an 18mm chipboard on between layers 2 & 3 -Condensation rate of 0.2g/m2h & Condensation rate 60days 284.2g/m2h. That seems significant but is it?

Seems a little barmy. I would have thought when you order the ICF you will take delivery of the whole quantity to build the house. Depending on your site, the best place to store this will be on your clean level slab. Why pour the ICF after one course? If you are hiring a concrete pump and ordering ready mix less pour days as possible seems sensible. I will be pouring ICF in two lifts, one at just over 2.8m and then again at wall plate height with gable.

Yep that's what I'm planning. I have left an additional 75mm clear of UFH pipes around the internal leaf of ICF. I will fix a scaff board down and the fix prop to the board There will be some fiddly areas to address such as corners where props overlap and the small porch area. I might just chuck down two layers of 18mm OSB in these areas.

Agreed. I had v similar condition and sent the LPA my own document which didn't spark any response. Of course the format was plagiarised from a similar planning application! Happy to send you both if you would like.

@Big Neil I've enquired but had no response from Pacific Aerobarrier regarding UK or European distribution. Could be an opportunity for someone to bring this product to market here if anyone is quick off the mark.

Have you got a machine handy? You could hire a riddle bucket

Do I need a specific ridge tile/slate to suit my needs? Front pitch is 45°, Rear is 16° then transitions to 45° Im thinking a half round would better absorb the transition. I'd like it to be seamless from the front that there is any change in pitch going on at the rear, if that's possible? It will be a 'dry ridge' to allow for ventilation

Interesting intentional use of rust streaks from nails

Significantly cheaper than Risinger but still effective https://www.instructables.com/id/Hidden-Room-Bookcase-Secret-Door/?utm_source=newsletter&amp;utm_medium=email

I'm in a similar position to you, self build mortgage on building only not land. Before the mortgage is granted I was required to submit a thorough costings including contingency. Once approved I was told I could have as much of the mortgage as I wanted. I have initially drawn a little under 50% and expecting this to get me to a water tight stage. Subsequent advances will be subject to another valuation and fee. To check the money has increased the value of the property! I will probably draw the remaining funds in one go so as to minimise hassle and fees of a valuation. However you only need to make repayments on the funds drawn so not much point having thousands sat in an account whilst servicing the debt. I am with Ecology building society who have been excellent so far.

Very true but Mr Ecologist has specified 'open loft space' cant be crowding the bat roost with trusses. Even an attic truss wouldn't satisfy. Lord have mercy!