Matt60

Would you use the same pump for the radiators upstairs too? I can see the logic in what you're saying, thanks. I am interested to know if my suggested system in orange warrants any further investigation? I do intend having a bottle fed open flame fire in the living room, but this is separate to the main house, accessed via a short half glazed link and with a vaulted ceiling with no rooms above it. I want a bottle fed fire as they are very controllable and I don't have to clean it every day and gather fuel etc.

Thanks, I see. The house I'm building will have 150mm fully filled cavities, 150mm Celotex over the block and beam floor, triple glazing and a zinc roof. I'm aiming for a high level of air tightness and intend on using a MVHR system, possibly with some sort of cooling function. I won't have the SAP report for another couple of weeks. Is my suggested system in orange no good at all then?

Hello, Thanks for your reply. It's a new build, foundations should go in at the end of next month. I have looked at ASHP and thought that if I had one I would just make it bigger than I need to be safe, but then I read that they short cycle if you do that. I like the reliability, speed of heat, and lack of servicing re the Sunamps systems. Is my suggested system in orange no good at all then? I had assumed that electric panel or fan heaters would be quite expensive. I would prefer it all to touch of a button ideally, or better still from my phone if possible. The PV has been in the mix from the outset, my south facing roof space is limited to 14 panels though which I make 4kw with high performing panels.

I keep trying to find an alternative to an ASHP as I would like a system that operates as quickly and to the temperatures of a traditional system. I have a few old injuries that sometimes need 23 degrees in order to feel comfortable and I'd like to be able to reach that from a sensible starting temperature with a couple of hours. My last oil boiler could do that but I'm building a new house and don't really want to put that dirty old solution in to an otherwise modern house unless I have to. Every time I think I've cracked it, I get a load of information that makes me doubt it will work. The most recent idea was to have PV panels (I can get 4 kw on the roof) and use them to primarily power a big Sunamp with any surplus going to a separate one to heat upstairs radiators. Additionally, I thought I might use 2 Willis heaters to power the underfloor heating. I made and online enquiry with my nearest Sunamp supplier and then received a call from someone who followed up his verbal tripe with the following by email which I have copy/pasted. I have put the parts in red that amused me the most; Good to chat with you, in summary: 1. Solar panels will only give you back around £200-300 per year, based on roof direction, and based on a 4kw system (max on a residential roof), adding a battery will help. I think you are probably looking at a 25-30 year payback, before you see any financial benefit. 2. Sunamp - instant hot water system is around £4000-6000 and can be ran off solar, but even without solar it is still an efficient hot water system to run. I am not sure about using the Sun amp to run wet radiators, personally the less water in the house the better, because water leaks are always a lot of trouble. 3. Underfloor heating - wet is not too expensive to run but when it goes wrong (and it does) it’s a nightmare as can flood the house. Electric underfloor heating is great but very expensive to run, and when it breaks down, it’s also difficult to trace the issue and involves ripping up floors 4. German style electric storage heaters / radiators - they are modern, slimline, energy efficient and totally controllable. They come on and off as you require via wifi and are controlled via an app. There is a lot of choice in regard to sizes and colours, and they come with a 30 year guarantee. Prices range from £800-1500 per heater typically. He sells items 2 & 4 only - you'd never guess would you... From what I have read, a 4kw system should provide 3400kwh per annum and I make that nearer £600 per year if you can use use all the power with batteries or a Sunamp. Is this right? Additionally, I'm not looking for or asked about "pay back". I'm happy to spend a few quid to keep my bills under control, not least in preparation for when I retire. Does anyone know if my above suggested scheme (in orange above) is a reasonable idea? The reason for me separating the two heating circuits is that the radiators would presumably need to run at a higher temperature that the underfloor circuit. The house I'm building will have 150mm fully filled cavities, 150mm Celotex over the block and beam floor, triple glazing and a zinc roof. I'm aiming for a high level of air tightness and intend on using a MVHR system, possibly with some sort of cooling function. I won't have the SAP report for another couple of weeks. My main drainage runs are in and services are being brought in on the 15th of March. I know or at least think I know what I'm doing for the most part, but bar far and away the biggest headache is choosing a heating system. Any advice re my suggested system or an alternative would be appreciated.

All that glass at the front will have a cost implication and if there is no view from the front, you'd have to ask if it's worth it. Plus, if it doesn't have a view, will it impact on your privacy? It's difficult to give too much opinion on such a basic plan and not knowing the setting, obviously, you will be highly familiar with all of these aspects and so it will be much easier for you. Secondly, the plan does seem to give limited storage for coats and shoes and so I wonder if you might gain from changing the first floor glass to a normal window and adding a pitched roof porch. It would give a bit more visual interest from the from the front, would provide storage for all your coats and boots, would stop visitors seeing straight in to your house and be part funded by the deleted glazing. It would also offer an airlock so all your heat doesn't disappear when you open the door for a parcel etc.

I see, thanks for the info - looks like a really neat job and the widow width to suit whole/half bricks is a really good idea. The more I know, the more I know I need to know...?

We had one years ago at a previous house and I think it was made by a company called Balmoral. It gave perfect service and very rarely needed to be emptied compared to a normal tank which we had at the house we moved to. The Balmoral one we had was silent and we only had it serviced once in 6 years which I think cost £70 but that was about 15 years ago. Our self-build is on mains but it wouldn't bother me at all if I was looking at a treatment plant instead, and it would probably be cheaper on an annual basis than mains (though would obviously take years to recoup the install costs before someone says). Well, that was my experience for what it's worth and I dare say they're even better these days. The only irritation ours gave was it was difficult to hide the hatch and the electrical box for it but it had been fitted by the previous owners and could have been done much better with some thought. That would be my advice, carefully consider where you position the tank and the control box if it has one. Good luck.

Great result with the planning - well done!

We submitted the forms, it was accepted as a self build and exemption granted.

That's interesting, I like the idea of check reveals, does this work best with UPVC windows as they have a thicker frame to take in to account the difference in aperture width? My build is specced with aluminium windows and I assume they have a narrower frame and so the check difference would be more critical? What was the check difference on yours? The angled reveals, was that achieved by just cutting the blocks? Sorry for all the questions but you've raised some interesting points that I hadn't even considered.

Thanks for all the replies to this thread, I really appreciate it, it's all much clearer now. I will go back to the architect and builders merchant and suggest separate concrete lintels to deal with the 200mm cavity in Dritherm 32. Thanks again. ?

Thanks, that's good to know about the full fill and its what my architect is recommended.

Thanks, do you know what the cost difference is?

This is all making much more sense now, thanks. Is R32 the same as Dritherm 32 and I assume that "batts" is battons which is still but bendable rectangle pieces?

Hi Peter, thanks for your reply. Yep, you're saying much the same as Joe90 has just pointed out. I don't know enough about this to have considered that they can be done separately but that does make sense. What didn't make sense was that my proposed 200m cavity being seen as some massive departure from the norm. Insulation? I don't know yet to be honest. It might sound like a bit of a simplistic approach but I'm just figuring on the wider the cavity, the more insulation and the better thermal efficiency. The following is what my architect has sent through with his note about the wall thickness at the bottom which I followed up with the builders merchant who also didn't spot the potential to use separate inner and outer lintels. The short answer appears to be Dritherm 32 which I think is the bendy stuff that comes in boards - to give it its technical description... New Foundations:- 450mm and 600mm wide C25 mix concrete trench fill type foundations under the proposed 350mm wide cavity walls. Foundation depths to be checked and confirmed on site by Building Control Officer. New Ground Floor Construction:- 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. 225mm min. ventilated void below. New External Brickwork Cavity Walls (350mm overall thickness):- 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):- 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):- 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):- 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):- 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):- 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):- 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. Please note that further to using 200mm wide cavities just double check with your builder or material supplier the availability of cavity walls lintels for this width of cavity as we don’t think there is many manufacturers that make a lintel that wide (400mm wide overall)?

Right, I see what you mean. I think they were talking about Catnic type lintels that do the inner and outer. Obviously you're saying that you've done the inner and outer separately which makes sense. Thanks for this, I'll go back to them and pose this as a point.

Right, I see, everything seems to be pointing to a 350mm wall with 150mm cavity. Now you mention it I think something was said about needing larger foundations. I guess that 350/150 is still a larger cavity than normal, but didn't expect the 400mm wall with 200mm cavity to throw up so many issues. Thanks for the reply.

When I started reading the House Builders Bible, he mentions going for a 400mm cavity wall as a compromise between passive house standard and reducing room sizes. I thought that sounded pretty reasonable and I hope to build to a semi passive house standard too. However, both my architect and builder merchant have stated that if I go more than a 350mm thickness I will have to have lintels specially made which will add to the cost of the build considerably. I have been told that up to 350mm is fine and that off the peg lintels are available for that. All of this struck me as odd given that passive houses have even wider walls and I didn't think that 400mm was particularly excessive by modern standard. Does anyone have any experience on this? Thanks, Matt.

Thanks all and sorry for not getting back on here sooner, I have been ridiculously busy since my post but now my house move is out of the way I should be able to concentrate on the build now. Thanks for all the kind comments and advice. To answer some of the points raised; We should be able to start in March 21, we already had full detailed planning passed, (we could have started building that plan last year) the current application is just amendments to the already passed detailed plans and the determination date is the 12th of March. The drains and services started to be dug and brought in from November. I can't ditch the zinc roof, it's part of the detailed planning and I know the planners will not allow it to be changed. There are 3 plots and my neighbour who is about a month ahead of us (footing poured last week) has already tried and failed with that. The cost will be about £20k more than slate and we made peace with that for the benefits and look. We have not considered living on site, we have 2 kids and a dog and we own a ton of stuff - we moved in to a comfortable rented cottage last week and it is 11 doors up from our build. Yes it costs more, but the alternative is not workable for us and with the current pandemic if I have to shut the project down for months at least we are all living in comfort. Situation re CIL? I'm not sure what you mean, it's a self build and has been accepted as such with a start date of November 2020 which is when the drain work started - we're not paying any CIL. Solar panels - we don't need a feed-in tariff, the excess power will go to the batteries. The batteries I can get are the correct type, 3 years old and warrantied for 10, I am able to buy these substantially below what they are new. I may be able to supply these in the future if anyone is interested, but not before I have the ones I need. I have a friend who has a battery bank from this same source which he has been using for 3 years now and raves about it. For every fan of ASHP, I seem to find 3 people who wish they hadn't. It seems to me that they can be noisy, unreliable and expensive to run. I've heard of people with £300 a month electricity bills to turn them in the winter and £1500 condensers failing after 18 months and a wait of 3 weeks to replacement. I have also been told it can be difficult to find many people qualified to service them and that this can be expensive too. I do also appreciate that they can work well in a well designed system with a well insulated and air tight build. I'm coming away from the idea of an electric boiler but not by much. I'm looking at a thermal heat store with 3 internal elements, powered by a combination of the solar thermal tubes, & PV panels/batteries to the internal elements. I'm looking at a bottle fed gas fire (wood burner look) with back boiler that will also contribute when in use and that would mean we could use that solely to heat the heat store if the electrical part of the system ever failed. With the tubes, panels and significant battery storage the top-up the system would need from the grid in the cooler months should be fairly limited to my thinking. This system also has only 2 central heating pumps as moving parts which are cheap and easy to replace and there are no service costs. The plan is to have under floor heating on both floors. I know this will not be cheap but I don't subscribe to the argument; "it will take 30 years before you get your money back"... I'd rather have an effective, cheap to run heating system than a £30k kitchen. I'm waiting for someone much cleverer than me to design the system and calculate how much it will cost to run. Thanks again for the replies.

Hello to you all, My name is Matt and I live in Norfolk with my wife and 2 young kids. We have completed on a plot with detailed planning permission and are currently having the plans re-drawn to better suit our needs and spec. Although we own the plot, we can't really develop it without selling our current house which should be completed by the end of January, at which point we will move in to rented for the duration of the build. The new house is a mixture of materials including a zinc roof, K-render, brick, with a slate roof to the garage section. It will be 2650 ft2 and will be a very bottom heavy 4 bedroom 2 storey house with a roof terrace overlooking the field views the the rear. My intention is to build to a semi passive haus standard and avoid an air source heat pump in favour of solar panels with a large battery bank and an electric boiler coupled with evacuated tube hot water system. While having the plans re-drawn, I have tried to reduce costs as far as possible, purely as I know it will cost us more than I think, as it does for all bar the most experienced house builders which we are not. The house and garden will be planned to make it as maintenance free as possible, me and my wife work full-time and want to make the most of every spare moment we have. We're hoping to get started in March 2021. Regards, Matt. We are completely new to this