BartW

Hi, I am after a bit of advice. I am currently sizing a system for our future home. Current facts: We live in a 2 bed maisonette at the moment. The two of us and a dog Factual 12 month energy use is 3000kWh (Jan '20 to Jan '21, so enough to stipulate 50% daytime occupancy). That is a combination of usual appliances, induction hob, UFH, and plenty of LED mood strip lighting. The current property is 70sq metres. The future: The two of us, and two kids, and (maybe) two dogs Property size 180sq m. Fully detached, 0.15uVal all around Timber Frame home, with all as the above, but also 7kW ASHP, MVHR, very open downstairs, and a total of 4 bedrooms (+gym on the top floor). Also some smart home gear (if money were to allow). Assumed 12month energy use 6000kWh. The following Roof: Assumed 10no 445W panels along the pitched roof (South - tiny-bit-East roof), and 6no 445W panels on the flat roof. All connected up using individual microinverters. No shading. Total 7120W @ 20% panel efficiency x 70% realistic efficiency due to weather, etc gives me 996W per h. If I average 7 hours a day in beautiful Oxfordshire, then there is a potential for 7kWh of energy. Paired with "alleged" 16kWh daily consumption, this is technically not enough to warrant a battery storage, BUT we all know that energy recuperation times are never equal the energy required, due to the lifestyles, and other factors. Take for example washing machine, and tumble dryer. These would usually work evening, or weekends. Would the battery storage help with the "energy management"? If so, would a 7kWh choice be optimal? I can only imagine that anything bigger would never get fully charged, unless we are on holiday. So with the above in mind, I can probably build a 7kWh PV with 7kWh battery for not a lot more than £7k + VAT. Am I being logical? Or a bit naive? Many thanks on this freezing mid Winter Sunday Bart

Ballast trays make me nervous about the panels taking off one day in the future... It will be a flat roof @ 8m above ground, not sheltered by anything around. A 2m long panel that only weights 20kg (plus whatever ballast weights) could still get some decent aerodynamics in a 100mph well directioned wind ? Here is our roof, and the potential it offers to solar PV. We would also want to install wooden rain screen cladding around the PV panels, seeing there will be little left of them.

Hi, I am thinking of using GRP roof on flat and pitched part. The plan is to then install PV panels on aluminium rails on both roofs. The question: Is there a robust detail that will allow penetration through the warm GRP roof? I thought perhaps do the GRP, then add C24 blocks, GRP over the whole thing again, and install the frame onto that. Would that work? Thanks Bart

Yeah, the notching was being considered, but that would mean I need to notch the structural part of the building, which I am rather not keen on. I get two layers of battens @ 25mm thick, behind the slate tile rain screen cladding, so in theory that's just another 20ish mm to notch, BUT.... is this asking for trouble somewhere down the line?

Hey, yes that was my approach, but it calls for some compromise. I am basically slightly uneasy about running the downpipe internally through the house. And quite frankly this is the only thing preventing me from just going with it. My 5th post from top here explains what I was getting at:

Yes, GRP was the way to go with this, but as you say it is a complete roof redesign. I have sat on it for a few weeks now, and general conclusion is that everyone apart from the looks speaks for something more conventional. So, the question is what to swap it for? I was going to have a clean transition between the pitched roof side and the wall. I am now thinking of adding a section of pressed aluminium gutter along the side that would hopefully disappear if done in matching black powder coat (on black slate tiles).

Hey how did you address your gutters on a TF construction? This is my last sticking point preventing me from finalising on the design. have you got any pics of what MBC designed, or what you ended up with? many thanks! bart

Hi guys, A quick bump in case anyone might be able to offer some advice on this?

Have you considered Cellecta Xfloo + screedboard20? Not sure about the refurb, but perfect for new build solution. Total buildup is 53mm.

Is that your roof size? Blimey, how big is going to be your house ??

I would love to, but I am hardly getting to grips with it myself ? I will let the veterans take a lead on that. I will happily listen, and read some more myself ?

Which part? it’s 80m2. Although I don’t remember why I allowed that much. The pitched prt of my roof is only 10.2m x 4m at the longest. I think I may have put a proviso for front and rear gable in that as well as the wall that’s holding the ridge. I basically quantified square metres @ 80m2 and deducted for the rafter part, hence the line above it @ 70m2. The predicted uValue is 0.13 when using the kingspan calculator, but I stipulated 0.14 when using cheaper PIR products.

Generally insulationshop.co for some products, but equally a lot of general google / online shopping for others. I did not write down the sources I was pricing these from (useful I know...), but was getting the below prices just from shopping. I did not speak to anyone, or any of my usual builders’ merchants, some of which I get better rates than others. I hope this helps: Structural walls insulation: M2 Supply only cavity insulation 210 Celotex XR4120 per 2.88 £38 £2,771 Supply only internal face insulation 264 Celotex GA4050 per 2.88 £17 £1,558 Supply only VCL 264 Superfoil VCL per 75m2 £85 £299 Supply only internal battens 456 Sawn Green 50x25 per 4.8 £4 £380 MIneral wool for intermediate floor + gym + loft storage 134 Loft roll 150mm Knauf 44 per 9.18m2 £20 £292 Structural roof insulation: Supply only deck PIR 77 Celotex XR4150 per 2.88m2 £50.00 £1,337 Supply only VCL 77 Superfoil VCL per 75m2 £85 £87 Pitched Roof insulation: Supply only PIR between studs 70 Celotex XR4150 per 2.88m2 £50.00 £1,215 Supply only PIR internally 80 Celotex GA4030 per 2.88m2 £13.00 £361 Supply only VCL 80 Superfoil VCL per 75m2 £85 £91 SUBTOTAL £8,391.43

I remember those times. 2 - 3 years ago I lost a small fortune to buying of 150sq metres of PIR for a domestic refurb / extension project for my client... Decrement delay, and other associated posts and opinions come to mind Really, I am down to choosing between PIR on PIR vs PIR on rock wool. Money seems not far off, although then the difference being: decrement delay vs wall thickness. I can afford the latter. Can I afford the former? Would I tell the difference?

Ok, So: - Frametherm 32 is a lot more expensive than 35, and only makes a difference of 0.005 u value. So my choice of the 35 version is deliberate (or call me cheap ) - with my buildup, as in the original post reducing the PIR from 80 to 70mm means going up to 0.1501 uValue. So I kept the 80 to stay on the safe side. - sounds like my choices are feasible? Why not use a single sheet of 140mm? Surely It is cheaper and quicker to do a single layer rather than 100 + 40? I omitted it because it was not making any significant difference. Also the program was getting confused with layers of free air and two lots of battens setting the slates, and the cladding off the structural wall. That was my original choice, but the decrement delay, and the fuff of precisely slotting bits of the PIR in-between the structural studs has me rethinking my choices. In an ideal world I would do rock wool throughout, but then the wall buildup increases beyond feasible (and so does the labour).

You’ve created an air gap for no reason..?? Seems no point to this build up. Sorry, I should have clarified. The what if scenario assumes doing both, not either or. I have. It was big money when I checked. I am assuming that is in reference to the above wall buildup?

Hi everyone, I am nearing completion of my (already approved) drawings, and am now down to a fine nitty gritty. I need to propose the drawings to the TF supplier, and with that in mind I need to make up my mind about the insulation, thus the external wall buildup. I have played around with all sorts of calculators, read the forum about the decrement delay etc, and... still no wiser. So I hope you may be able to give me a final steer. Some basic facts: - we need to achieve 0.15 uValue - we are building using a TF construction with 140mm studs - TF supplier will supply the frame, erect, and VCL all around - insulation and internals are down to us - externally we are having a combination of natural slate from Cuppa Pizzaras and Sliva Birch clad as 44mm vertical battens My considerations: - PIR helps achieve the driven uValue with a smaller buildup - PIR is flammable right? - PIR has lower decrement delay - packing PIR tightly is more challenging to unskilled - mineral wool is better to handle, and transport, store on site, etc - in order to achieve 0.15 I would need to use layers of rockwool, if on its own - the build has got a budget cap, and I worry that layers of rock wool will brake the piggy bank, and add a considerable amount of time to the build What if: - I use 150mm packed rock wool in a 140mm stud (is it a healthy thing? Would that give a benefit? Or should I stick to 140 / 140) - put a single layer of PIR internally @ 80mm I did some calcs, and I seem to be achieving as per the below: Am I on the right path? Of course, I would love to be doing things "the proper way", but money is a detrimental factor here. I hope just by building and not giving in to poor quality mass developer builds, I am already "making a difference" On a separate note: I am trying to design a balcony / terrace roof insulation, and whilst I am ok to have a step up from the bedroom to the terrace (above the dining room), I wonder if I could be doing this slightly differently. Currently, getting at a typical warm roof buildup with OSB/PIR/OSB, all upon rafters. Could I reduce the thickness of the PIR above to, say, 50mm, pack rock wool in-between rafters, and finish off with a insulated plasterboard? That area of ceiling is less than 10m2. Similarly, we are having a section of a pitched roof that will be clad in natural slate. Is doing the PIR between rafters + PIR under the ok way to do it? I wouldn't necessarily want to increase the roof thickness beyond what's required. Many thanks! Bart

Yes, the thickness of the roof buildup above the dining area / below the terrace is certainly something that will need drawing up in detail. There are a few things I am considering: - Kingspan TR26 for structural roof terraces - thinner joists in that area - as you stated, bulkhead dropping down over the dining area - inverted / hybrid roof insulation design And quite possibly a combination of all of the above. As for the staircase, it is the very vague quality of the planning drawings that I am refining as we speak. The finished ceiling height on ground and first floors will be 2400mm. By pushing a step forward I am achieving it within 13 steps, and end up with a decent 1030mm long landing. Regs say at least as long as wide for the landing. I wonder if I may be able to get away with a narrower staircase to the top floor. At the moment I am proposing 900mm wide. Every little helps, they say, to get the room back to the Master Bedroom. Quick snippet attached below:

Thanks. It is in fact one of the things that are doing my head in right now. How to / where to / stop the wood cladding, what to turn it into etc. Rain water falls and all other likes. I am slowly turning these concepts into a working set of drawings. Hopefully should have it completed in a week or two (of my sleepless design nights ) Bart

Haha thanks, priorities change with age, and I am going to ensure there is enough future proofing in case it ever becomes a man cave with private terrace for private parties

Hi, yes thank you. I have some visuals and elevations to accompany. see attached. Bart gh pl250 front and rear elevations rev b.pdf gh pl250 side elevations rev b.pdf

sadly, that is one thing to keep me sane after a long day at work, so a gym is a must ? we were gonna have it as an outbuilding in the garden, but decided it would be better to have it at home, free up the already small garden, and add a terrace to it too. first world problems of course ?

I was assuming from start that: - downstairs loo might need adjusting in width, thus affecting the Guest Bedroom - open plan everything might call for sprinklers. Similarly the staircase. I read BR back to front for things like sizes of the stairs, clear passages, dims, etc, so was assuming little else may have to be changed. External elevations being a combination of natural slate (non-comb) and wood slats might call for additional product treatment. All in all, I was not expecting anything else to be made to undergo any drastic changes, hence submission and approval of plans as shown. or am I missing something substantial here? ?

I suppose this is where having a "real architect" comes in handy...

Hey, the stairs from ground to first are as follows: stairs from first to top floor as below: Bart