Matt60

Thanks for the info, I'll feed that back and see what they say. Yes, the drop in height from the house to the garage has been accounted for thanks. Ignore the screed thing, that's me not him, he said R35 concrete, I just lose my way with all the different terminology. Where did you get your tiles from, are they any good, could you jack a car up on them without damage? Thanks again.

Will it work with a screed that thick? This question relates to the garage/workshop part of my new build only, the rest of the house will have the standard 75mm. The architect and structural engineer both know I wanted to have under floor heating in the garage and workshop because I spend a lot of time in there, particularly in the winter. However, in order to take the weight of a car, the screed needs to be 150mm thick and the SE has asked if my plumber (not selected yet) is willing to lay his system in this with the metal mesh that the SE has also specified. To quote the SE; "We would usually suggest a 150mm thick, RC35 slab in garages with A193 mesh in the middle." My immediate reaction to that question is; "Will the heat get through a slab that thick?" I don't need the garage to be house warm, on my old garage I used to heat it to 7 degrees to stop it hitting the due point and then just use a fan heater to top-up when working in there. I wonder if I might be better with a couple of big radiators with no trv's running as a slave on the ground floor UFH system. By that I mean say set the house to 22 degrees and the 2 garage rads would produce some heat as a by-product of the house reaching and maintaining 22 degrees, as the system effectively wouldn't know about the garage rads, which would mean the system is not trying to hit a target for the garage but should keep it above the due point. Then I could just top-up with a fan heater like I used to. Any guidance is appreciated, I need to go back to the structural engineer ASAP so he knows if the mesh is needed. He's specified the steel mesh just to stop the UFH cracking the screed but it won't be need if I go with rads or something else. Thanks.

Thanks, would I be able to to do this and have the upstairs heating circuit running at a higher temperature than the UFH on the ground floor? I don't want UFH upstairs (two professional house builders I know have said it's more trouble than it's worth) and I'd rather avoid having over-sized radiators too. It's possible that even if they ran at the temp of the UFH it would be enough with the thermal efficiencies of the build, but I'd like to know if I can run the tank, UFH and rads all from a ASHP with all three requiring different temps.

Thanks, I think this is probably the way to go and with a very low initial outlay. If at a later date an ASHP was fitted, would you aim to use it just for the cylinder or to replace the Willis heaters too? I guess some PV and a battery would be good with this too if the cost is justifiable?

One option that I am researching is a thermal heat store with 3 internal emersion heaters which is also connected to solar thermal tubes. The latter should heat the majority of the thermal store during the summer, but I'd like to also link in a bottle fed gas fire with back boiler that would take over from the solar thermal and limit the amount of immersion heating required in the winter months. Despite searching, does anyone know if you can buy a real flame, bottle fed gas fire with a back boiler?

Pretty much exactly what I'm think except supplemented by PV and a battery bank to take the edge off the yearly cost. That said, the PV and battery could always be retro fitted once running costs are established. I intend to have a bottle fed gas fire with back-boiler (can clain the VAT back as it would be part of the hot water system) which will heat much of the hot water in the winter. I also wonder if instead of an immersion heater and willis' if a electric boiler would be better to do both?

Thanks for your reply, that comes out at approx 4kwh on that link from PV. My current (last house - now renting while building) was on oil and so the bills on that won't help me much as both heating and hot water was via the oil. What I'd like to know is how much it would cost to heat and do the hot water via emersion and electric boiler in the new house. If I had an idea what that would be I just need to subtract the afore mentioned PV contribution and then I can assess it against other systems.

Thanks all. @newhomeI think my concerns and attitudes would be much the same as yours in the same position. It's an interesting consideration as If I just when with emersion heater and electric boiler I would save thousands on installation costs and have a silent and fast system with no maintenance. I'm more open to this (probably coupled with PV and a battery bank) than you might imagine. If I spent out on panels and a battery bank, I reckon that would save about £600 a year and so I wonder how that would stack up cost wise to run each year.

Just re-posting the above as the thread went off at a tangent for a bit and I'm interested to see what alternatives people have used and would recommend. Ideally, I'd like 2/3 options to fully research and pick the bones out of. The heating and hot water is the issue that I'd must like to get decided on. Many thanks in advance.

Thanks for that, very useful info. ?

Good to know - thanks! Do you mind me asking what you pay per month in electricity and if you have any PV?

I suspect this is spot-on. My last house had very noisy floorboards, when all the carpets were replaced I put loads of screws in and it improved massively.

Jesus Christ fella's!! I only stepped away for a few hours!! ? Thanks for the info on the render/plaster coat. I think this is what I'll do as well as a slurry coat between the floor joists - thanks. Oh, I don't have access to gas I'm afraid. I am happy to consider a ASHP, though I do have some reservations, but contrary to an earlier suggestion, I do want radiators upstairs and UFH downstairs. I know 2 professional house builders and both have said that upstairs, with a timber floor, the noise associated UFH expansion and retraction is not worth it. I saw in another thread on here somewhere some radiators that can be run with an ASHP that blow hot or cold which on the face of it looks almost too good to be true. I would like to use PV preferably using or storing all the energy from it and not exporting at all to the grid. This is why I was originally considering a Sunamp - stores energy and avoids buying a battery bank. I do like the idea of being able to cool, especially as it would probably be very cheap in the summer with the PV. Either way, gas is not available and I'd just like ideas of alternatives that will provide plenty of heat without costing a fortune to run and not be too horrendous to purchase. I'm interested if anyone has good experiences with anything else, ASHP's are often the most obvious choice but I don't want to just assume it's the best solution open to me. Thanks for all the input.

Yeah I got that and would do if I went with the slurry coat. What I need to know is with a render coat, would most good plasterers be able to do that? The latter would be my preference for the reasons @joe90 said. Thanks.

Thanks for all the replies here, there is some really useful stuff, I will definitely use a cement slurry or render and plaster coat rather than just straight dot and dab. Would a plasterer be able to do the render coat, presumably most good one would?

I see, that makes sense - thankyou.

Excuse my ignorance, genuinely, but how would it cause problems?

Would this be good to use? Tanking Slurry Waterproof Cement Based Coating 20kg | Builders Merchant Direct (bmdgroup.co.uk)

Do you just mean plaster straight on to the block work?

Thanks for all the replies, I really appreciate it and there's some interesting points there and It highlights that I have been a bit lazy really. Using the supplied link on one of the above posts I can find single skin Catnics which appear to solve the problem very easily. That said, if I go for the 200mm cavity I'll need a wider footing which adds a further complication and cost. What I'm gleaning over all from the above is that the difference in U value between 150mm and 200mm is not actually that great, but that in either case, the dot and dab is a real risk to air tightness. What I can say is that every time I have spoken to the bricklayer I have told him that I've seen blocks laid with gaps etc and that I won't accept that at all. I have made it clear that I am looking for air-tightness and I expect every brick and block fully sealed with mortar. Aside from anything else, it looks awful and I have never subscribed to the "you don't see it" school of thought on anything. It's like trades who leave ceiling voids full of crap - there's not reason to do this imo. What would you suggest instead of dot and dab? My last house was a 1985 place built as a pair by a local builder, it was heated by an oil boiler. I can't help but wonder with the efficiencies of the new place if an oil boiler might make sense? I'm not all that keen on putting such an old fashioned solution in but it would be cheap to install and produce enough heat. Thoughts?

It's not me that is hung up on anything, I know sod all about this. I have an architect, bricklayer and builders merchant who have all independently said the same thing, and I do not have the knowledge to challenge it or suggest an alternative, though I have suspect there are some from the outset. I get what you are saying re brick arches, I think but cut bricks into slips when glued.... not the foggiest. Yes please, do post - simpler the better, nothing to prove, I know lots about stuff I like and need to know to earn a living, but very little about this. ?

Such passion - love it!! As I have alluded to before, I tried to go 200mm cavity, but you cannot get an off the peg Catnic to span that distance and paying a structural engineer to calculate every aperture for steels looks very expensive. @joe90 has kindly offered that he has used brick arches and concrete lintels, but I will have a couple of sets of bi-folds which would be too wide to use this as a solution. I think? I'm not about to become that pain in the arse client, and so I will stick with the values above for better or worse. With that in mind, I would still be interested to know what systems people would use. ?

Thanks for all the replies, I appreciate it and as I've said before, the heating is the biggest worry I have for the whole build to be honest. My architect has come back with my U values today which are a bit better than some of those estimated, I'll post the spec below. So to turn this thread on it's head, with the following values, if it were your house and you don't like the cold - what system would you fit? For clarity, don't denigrate someone else's system - what would YOU do? I will read and research any suggestions. Again, thankyou for your responses and thankyou in advance for the systems you can suggest. My specs; New Ground Floor Construction – U-Value 0.12 W/m2K:- 75mm sand / cement screed. Selected underfloor heating to be installed within screed. 500 gauge separating layer. 150mm Celotex XR4000 insulation. 1200 gauge polythene DPM. Selected 150mm deep PCC beam and block floor. 150mm min. ventilated void below. New External Brickwork Cavity Walls (350mm overall thickness) – U-Value 0.18 W/m2K:- Selected 103mm brickwork outer leaf. 150mm cavity to be fully filled with Dritherm 32 or similar approved insulation. 100mm Durox Supabloc (3.6mm2) or similar approved blockwork inner leaf. 12.5mm Gyproc Wallboard on dabs with skim coat finish. New External Rendered Cavity Walls (350mm overall thickness) – U-Value 0.17 W/m2K:- K-Rend render or similar approved render. 100mm Hemelite Standard (3.6mm2) or similar approved blockwork outer leaf. 150mm cavity to be fully filled with Dritherm 32 or similar approved insulation. 100mm Durox Supabloc (3.6mm2) or similar approved blockwork inner leaf. 12.5mm Gyproc Wallboard on dabs with skim coat finish. New External Boarded Cavity Walls (350mm overall thickness) – U-Value 0.16 W/m2K:- Selected composite boarding to be fixed into 25mm or 38mm x 50mm tanalised timber vertical battens. 100mm Hemelite Standard (3.6mm2) or similar approved blockwork outer leaf. 150mm cavity to be fully filled with Dritherm 32 or similar approved insulation. 100mm Durox Supabloc (3.6mm2) or similar approved blockwork inner leaf. 12.5mm Gyproc Wallboard on dabs with skim coat finish. New Pitched Roof (Vaulted Ceiling) – U-Value 0.18 W/m2K:- New zinc roof to be fixed in accordance with the manufacturer’s instructions on a selected underlay. 18mm WBP ply or OSB/3 to be fixed into timber rafters / raised tie roof trusses. 50mm min. ventilated air gap between the Celotex insulation and breather membrane. Insulate between rafters with 100mm Celotex XR4000 insulation or similar approved. Insulate under the rafters with 40mm Celotex TB4000 insulation or similar approved. 15mm Gyproc Duplex Wallboard (foil backed) with skim coat finish. New flat roof (Warm Roof) – U-Value 0.16 W/m2K:- Selected single ply flat roof membrane. 18mm WBP ply or OSB/3. 120mm Celotex XR4000 insulation or similar approved. Vapour Control Layer (VCL). 18mm WBP ply or OSB/3. Flat roof joists (sizes to be determined by Structural Engineer) 15mm Gyproc Wallboard with skim coat finish. New Pitched Roof (Flat Ceiling) – U-Value 0.11 W/m2K:- New zinc roof to be fixed in accordance with the manufacturer’s instructions on a selected underlay. 18mm WBP ply or OSB/3 to be fixed into timber rafters / raised tie roof trusses. Raised tie trusses. Insulate between the ceiling joists with 200mm fibreglass insulation and 200mm fibreglass insulation to be cross laid over. 15mm Gyproc Duplex Wallboard (foil backed) with skim coat finish. New Pitched Roof (Above Garage / Vaulted Ceiling) – U-Value 0.19 W/m2K:- Selected slate tiles to be laid in accordance with the manufacturer’s instructions on 25 x 50mm tanalised timber battens. Selected Tyvek or similar approved breather membrane on attic roof trusses. 25mm min. ventilated air gap between the Celotex insulation and breather membrane. Insulate between rafters with 150mm Celotex XR4000 insulation or similar approved. 15mm Gyproc Duplex Wallboard (foil backed) with skim coat finish.

That's interesting and I have plenty of space for a cylinder, I was more thinking of the Sunamp as way to use all the PV energy. I'll look in to that, I'm not keen on the fan heater though tbh, I'd like it as a nice neat centrally controlled system if possible. The insulation is Dritherm 32, I suppose that is mineral wool. I could just about change it, I originally asked for a 200mm cavity but the architect, bricklayer and builders merchant all said it would cause issues with Catnics that could span a 200mm cavity. When I suggested separate steels or concrete lintels I was told it would be costly to have the steels as they would all have to be individually calculated and the steel supply could delay things. The builders merchant said there is no off the peg Catnic type steels that would suit.

Is a Sunamp considered resistance heating or would that give similar numbers to to the ASHP? I have just got time to change this and I did discuss it but I was told that it needs to be in multiples of 75mm to match the brick courses. 225mm would be difficult and 300mm a bit excessive and expensive?