Roger440

Im in the same position. Without ANY insulation under. I intend to do likewise, just set it into the existing concrete. Of course, its a long way from ideal, it will cost more money to run than if it has proper insulation. Quite a bit more. Its all very well people saying dig up the floor, but that costs. A lot. I ran some crude numbers. Id need to live to well over 100 years old to see payback. Not happening. Got better things to spend my money on. The reality is, its makes no economic sense. Unless you are 12. Dont take my word for it though, crunch the numbers yourself. Use the Jeremy spreadsheet on here to help figure it out. Id imagine with 25mm insulation under, your payback will be even longer. Of course, it will be better done right. If i had unlimited funds id do it right.

You make a good point. Wasnt aware i can hang it out as long as it takes me. Which would indeed be quite a while! I do still have the issue of cost and risk of doing it with approval, which, seems, unless someone says different, inescapable.

Im intending to die here, but that may not pan out, so yes, when selling it can be an issue. Traditionally an indemnity policy is peanuts, because the risk of action was essentially zero. I bought this house in the full knowledge that nothing that had been done, boiler aside, had certification. My previous house proved that such certification, of which there was plenty, was to all practical intents, worthless. Had i relied on it as evidence of compliance i would have been most disappointed. But, yes, going forward, logically those indemnity policies will go up in cost as the risk of enforcement increases. But to get to the nub of it, if it was just the BC fee, that would be OK. But its not like i can present my sketches and say, i want to do this, is that OK? Unless ive very much misunderstood, im going to need "proper" drawings, SAP assesment, maybe a WUFI condensation risk analaysis for the walls. None of these will tell me anything i dont already know. However, i cant do any of these things myself. Things things are not £50. So i either spend significant sums on these things, with no guarantee of acceptance as i am departing from the regs, and the risk of further reports and / or changes to what i can do. Then ill have to do the same again later when i do the windows. And the back of the house, the cavity wall bit. Each time another 4 figure sum. It makes no sense to keep shelling out for things that add nothing to the house, for a project that even without those additional report costs etc is way beyond the 15 year payback period to which the regs refer. Essentially, my choices are do it by the rules with lots of extra cost incurred, with no certainty what the final cost will be, just do it with out approval, or do nothing and buy more oil (which is the financially sensible option). My takeaway so far is that i could probably get approval for my plans, but at considerable additional cost. Cost which adds nothing to the final result. Though im struggling to believe anyone will let me do UFH on an uninsulated slab?!? Im conflicted given the new penalties...........................................

Anybody have any thoughts on my random scribblings please?

Indeed, you have suggested this previously. I like the idea, though at a practical level there are some challenges, mainly the purlins that run along the roof blocking said airflow. And the roof is heavily shaded after midday/ early afternoon by 30m conifers. But ive not abandoned the idea. I did originally start a thread on how to heat the place at zero or close to zero cost.

Because im an idiot, i miscaluclated where the door would land, mainly because i changed my door solution post slab laying, but if we ignore that aspect, i put 2 inch EPS on the upstand where the door was, then cut it back at an angle so the block paving could run up to the concrete. So yes, something of a thermal bridge there. Could have put a thin sheet of something in the gap to actually break the bridge though.. Like a thinner GRP box section. Perfect, no, but light years ahead of any other garage i have had.

Yes, i mentioned that in my other thread about my house, which is why ive considered involving a BCO, where, normally i wouldnt. 2 years inside for fitting a window seems like overkill V the offence. How dare i. I should allow someone with a can of squirty foam, but sporting a fensa certificate to do a crap job instead. For my barn/shed call it what you will, trying to comply means costs approaching 100k. Its just a (big) workshop for my cars, toys and stuff. Not happening. I can of course make it much better for circa 20k, but that wouldnt be allowed. Even at £20k, its cheaper just to burn diesel. Id just prefer it stayed warmish at a more constant level, as it will be better for the stuff in there, and means it wont be freezing cold when i go in there in the morning. Takes a coule of hours for the blower to get it from zero to 12c.

With a sustained cold period very! Same as outside pretty much Walls are block cavity, so that slows things down, but is just cement board roof. Ive got waste oil burner with blower that i now run on red diesel, but that makes for expensive warnth!

In mine, with its completely uninsulated roof, its always noticeable warmer up near the roof. Pushing that air back down is almost free. Yes, OP seems to have disappeared? Shame as it looked interesting.

Yes, sadly the whole building regs issue comes up. Given the proposed insulation by the OP, im guessing thats the requirements for a commercial building as it clearly is less than domestic. I wont comply as to do so would be prohibitively expensive. The roof for mine, just the roof, came in at circa £50k. Id have to live until im 300 years old to see any payback. As always, the requirements put you in an "all or nothing" situation.

Circulation fans will be essential, and useful whatever else might be done.

I had EPS up the side of the slab. It was steel framed with insulated steel composite panels. So the panels were screwed to the frame. The inner steel layer is inside the the envelop. The insulated parts sits on top of the EPS, and so the outer steel layer is outside. Yes, the securing screws are a thermal bridge, but thats inconsequential id suggest. So no thermal break in the envelope

Hmmm, this is interesting. I too have a 3000sqft "warehouse" that is my workshop with some accomadation built in. The accomadation is insulated all round with 50mm PIR so not great, but OK. I want to keep the main area at 12c over winter. But without it costing a fortune. Ive spent ages going over all sorts of options, for insulation and heating, so far with no decision. The accomadation is currentl;y direct resistance heating which is bankruptcy inducing to use. All this talk of draughts is valid for your regular commercial building, but can be overcome with good attention to detail with the insulation. Its interesting that, almost universally in the UK, warehouses are unheated, with local radiant heat for operatives at packing stations etc. However, our owning company in Poland, their warehouses are all heated to 16c. Unsurprisingly, they are all heavily insulated. Pretty normal there. Ive also visted sevaral in germany, including a couple of huge ones. All heated. It can be done.

When i built my insulated garage, nobody understands why, so i feel your pain. My answer is why would you build an uninsulated garage. If you are going to spend any time in it, or store anything remotely valuable in it, then it needs insulating. If you are not going to do any of those things, why builld it al all!

This is excellent. I should have asked here about the foam glass insulation but already asked on your other thread.

What ewas the reason for the foma glass? Ive used it , so am familiar with it, just not sure why in a new build garage? When i did mine, i created an insulated bucket of EPS to put the concrete in, so like yours an insulated slab.

Having used seconds and co a couple of times, the stock i bought showed no discernable issues aside from the odd chipped corner. Id have no hestitation doing so for something like this. For both layers.

Interesting approach (get it!!) I failed to come up with a solution on the garage i built at my first house, and so had that big thermal bridge. Was never happy with that.

Or hardcore/stone (thickness dependant on ground) with sand blinding. 150mm PIR, 100mm concrete. Even less digging. Only negative if you can call it that is slower response time on heating. Worked fine for me in an old house with uninsulated walls. It just sat at a constant temp all winter. Without knowing the foundations situation less digging = better in my world.

Agreed The work signed off in my case, was, afterall, done by the developer not the BCO But it was signed off by the enforcers of said regs. At best it was gross negligence, maybe corruption, but i cant prove that. I guess my biggest issue is that there is no comeback on the inspector. They cannot be held responsible for anything, unless you have extremely deep pockets.. Which is of course why we are where we are with the latest round of changes. And why i question the value of the process and the certificate. In my case it wasnt worth the value of the paper it was printed on. Anyway, this is largely a diversion

Ok, heres some crude sketches of my plans as they stand at the moment. As you will see, the back of the house is cavity wall, not solid. Ive not worried about this too much at moment as this is a bit more conventional, though still going round in circles re EPS beards. The insulation system referred to is: https://woodfibre.co.uk/internal-wall-insulation-iwi-28-w.asp Hopefully its mostly self explanatory? Any comments welcome.

I think you may have taken that out of context a touch. If im going to do something that either complies, or in this case is otherwise acceptable, then it is fact that it adds cost. It doesnt add anything beyond this. The overall outcome isnt "better" in any way because they are involved. Their additional cost in isolation isnt that big, but the costs of generating drawings, SAP assesments and whatever else they ask for all start to stack up quickly as these are things i cannot do myself. All to do something that is a well recognised solution to insulating an old stone building. I would however take issue with the assertion they keep standards high. From my limited experience, its been anything but as i have previously posted. The latest round of changes to the system reflect the fact it wasnt working and standard were not high, ie, like my old place, where they were happy to sign off any old crap. Indeed, stuff that wasnt actually there. Im not in any postion to have big arguments with them as its not my specialist field of knowledge, so am really keen not to find myself in that situation. Nor can i "add budget" to the job, as indeed you might as a professional in the field. Off to do some sketches.

i will do some sketches and post them. They will be just that though, sketches. You are a professional and in the trade. A BCO is rather more likely to take notice of you, than a DIYer like me. My, limited, experience of BCO's hast been a good one. Hence i now, in the recent past, simply havent bothered. Its adds nothing except cost to the end result. And I wasnt concerned as there was virtually no risk of any enforcement action. Thats seems to have changed. One question before i go and do some drawings, your discussions with the BCO, do they still do that? Under the new regulations, my understanding is they can no longer offer advice and suggestions? (or at least are not supposed to).

Currently, it's cheaper to buy oil than to to do the work. Based solely on the financials, no rational person would do anything. However I do prefer the increased comfort from said insulation. Yes, you are correct that the BBA certification should be ok, but often isn't with some of the less mainstream stuff. Essentially though, if I understand correctly, I will need to pay for drawings plans of my proposed works, bearing mind until I strip everything, I don't know for sure what's there, in order to pay for an sap assessment. Just guessing, but what, £2-3k in reports before I've done any work? Assuming it all goes to plan and there's no surprises that require the reports to be reworked to reflect reality.

I may not have explained myself well. I'm sure the report will be fine for the proposed works. My concern, given the construction method of the house, is I will need to use something like wood fibre and lime plaster, for example, which, clearly, many BCO's dont understand and/or are unwilling to sign off. Under this scenario you then have to go round the loop again with an alternative proposal . Repeat until agreement is reached. What the going rate for such an assessment for a whole house project? I've never done such a thing. I assume I'm going to need to provide a detailed plan/drawings for them to work from too? So another person to pay.