Total new heating system for a 5000sqf house

Cks5

Hi, I'm looking for some advice on heating a large new build up north
House was originally part built approx 5-6 years ago and is basically a bare shell and not as well insulated as I'd like.
Basically block built 100mm pir cavity, only room in the floor for 100mm pir, but I'm trying to see if possible to raise door heads to all more floor insulation, though external doors are Already fitted. Will fill the attic with min 300mm.
Block internal walls and concrete slab 1st floor
Have considered everything thus far, pellet boiler, heat pumps even oil!

We want to go with ufh at least downstairs , poss rads upstairs or ufh on both floors

We will be trying to make the house as airtight as possible
Pilkington insutherm/insulight hardwood windows, not sure of exact u value, but pretty good

What should I be considering here as we hope to start work end of jan
Cheers all

BryanF

Hi welcome to the C&P forum. Everything is possible but your expected budget and floor to ceilings heights are needed to comment

Cks5

Thanks for the welcome
Budget , haven't got a set idea on costings to be honest but it's something I want to get right

Ceiling height will be standard height, apart from 1 double height sunroom
6m x 4m
Suspended ceilings still to be fitted

BryanF

Well if you've a standard fl to cl with space for 100mm max PIR, it looks like you should forget the ufh. As regards air-tightness what ventilation system is proposed and what space has been allowed? re air-tightness it's probably worth testing before you go much further. And if you were in a position to temporarily heat the house on a cold day a thermal imaging assessment might be revealing

Edit: 5000sqft do you have 20 kids?

Cks5

BryanF wrote: »

Well if you've a standard fl to cl with space for 100mm max PIR, it looks like you should forget the ufh. As regards air-tightness what ventilation system is proposed and what space has been allowed? re air-tightness it's probably worth testing before you go much further. And if you were in a position to temporarily heat the house on a cold day a thermal imaging assessment might be revealing

Edit: 5000sqft do you have 20 kids?

To be honest we haven't decided on any of those options as yet and are hoping for various opinions and experiences
The house has yet to be sealed in any manner, gaps below and above external doors. The house is a total bare shell, walls, roof and windows

Just the 3 kids !

mark_18tp

Just read the all the posting.

Air tightness is key and Insulation. 5000sq would be ideal for heat recovery ventilation and with the suspended ceiling not fitted yet give consideration

have you any fuel available to you- e.g. wood etc.

also biomass (wood pellet) have payments 7 years at the minute and grant of 2500£ towards install.
very efficient and with the 7 year payback should pay for itself

pv panels have payment scheme for the next 20 years, i know this is coming to a end soon

Cks5

Thanks for the message.,
Insulation we are limited as to what is already fitted and the floor depth.
I would have liked to have doubled the already fitted insulation but that is not viable unfortunately.

I have looked at everything heating wise, inc pellets boilers & stoves , ashp and gshp., Nothing is jumping out to say yes this is what to go for 100%.
I do have access to a little wood, but not tonnes and tonnes of it.


I think the Solar PV is being extended to approx. October this coming year, it was supposed to end in April.

I am trying to read up on air tightness measures but there doesn't seem to be a lot of detail online, apart from basically filling any utility holes, gaps, sealing around doors, windows etc. Surely a wet plaster finish would give an airtight barrier around internal windows
Caulking skirting, floors etc

mark_18tp

well in my opinion

i would go for a pellet boiler, and have a accumulation tank, maybe even a oil boiler as back up so if it fails then your not left without heat, as for previous experience if a pellet boiler fails getting a engineer is a waiting game.

for heat recovery vent to work the house has to basically a passive house therefore you can't do that as your cavity isn't up to it and well its a decision that needed to happen at the start off the build, i know you can go around a fill gaps but to tell the truth a air tightness test would need to be done by a professional company (-snip-do air tightness testing maybe worth a call)

the only reason i asked about wood/ other fuel is maybe a gasification boiler would suit but since you don't have much lets scrap that idea

so ashp and gshp they work at low temperature so only really suited to ufh and will if you are thinking of putting 1 rad in the house these will not give you what you what except larger electricity bills

you can put more insulation on the internal walls and batten out, seen it done loads on old farm houses.

whatever you go for it has to work for you.
remember the ufh is completely different than conventional radiators and does require to be on nearly all the time.

Cks5

We had originally decided on a Pellet boiler, then came round to the idea of a ashp or gshp ( have the space ) with solar pv to cut down hopefully a hell of a lot on the added electric cost.
I would like ufh throughout, wife prefers rads and the idea off on / off heat. Personally I thought rads and oil would cost a fortune to run for the sqf of the house, not so bad if it stayed at current costs though !
I do like the idea of the grants and basically free heat for 7 years. Its just deciding on which option to plump on.
Do you go rads with oil or pellet boiler
Do you go ashp or gshp with ufh with buffer tank
Do you go ufh with pellet boiler, possible rads upstairs with buffer tank, as we are hoping we wont need a lot of heat in the bedrooms.

Yea we had ruled out heat recovery due to the insulation levels not being anywhere near passive standards

Condenser

Cks5 wrote: »

We had originally decided on a Pellet boiler, then came round to the idea of a ashp or gshp ( have the space ) with solar pv to cut down hopefully a hell of a lot on the added electric cost.
I would like ufh throughout, wife prefers rads and the idea off on / off heat. Personally I thought rads and oil would cost a fortune to run for the sqf of the house, not so bad if it stayed at current costs though !
I do like the idea of the grants and basically free heat for 7 years. Its just deciding on which option to plump on.
Do you go rads with oil or pellet boiler
Do you go ashp or gshp with ufh with buffer tank
Do you go ufh with pellet boiler, possible rads upstairs with buffer tank, as we are hoping we wont need a lot of heat in the bedrooms.

Yea we had ruled out heat recovery due to the insulation levels not being anywhere near passive standards

Is 100mm in the floor the total for insulation including screed or is it 100mm plus screed?
If its plus screed and you have another 60mm to play with then you'd be fine to fit UFH. Even at 75mm insulation plus screed you'd have very little heat loss through the floor. Certainly not enough to put me off using UFH if that's what you want to use.


I'd only use UFH if using a heat pump however as the comfort is much better as are the running costs. Only use a heat pump if you're using UFH throughout. No mixing and matching rads and the UFH should contain a high density of pipe and short loops.
Only use a GSHP on a house of that size. The jump in electricity costs with an ASHP in cold weather would be substantial and runnings costs for the GSHP would be far superior in general.
You don't need a buffer with a GSHP unless you have stats and I generally wouldn't recommend using stats with a heat pump.


Have you any space left in the cavity? Have you looked at BASF walltite? It could be a good solution to increase the U-value and airtightness of your walls.
Insulation normally is a separate issue from insulation. A well insulated house does not mean an airtight house and airtightness is the issue you must address regarding HRV. If you don't have a high degree of airtightness HRV is pointless.

BryanF

Cks5 wrote: »

We had originally decided on a Pellet boiler, then came round to the idea of a ashp or gshp ( have the space ) with solar pv to cut down hopefully a hell of a lot on the added electric cost.
I would like ufh throughout, wife prefers rads and the idea off on / off heat.

1. Personally I thought rads and oil would cost a fortune to run for the sqf of the house, not so bad if it stayed at current costs though !
2. I do like the idea of the grants and basically free heat for 7 years. Its just deciding on which option to plump on.
Do you go rads with oil or pellet boiler
Do you go ashp or gshp with ufh with buffer tank
3. Do you go ufh with pellet boiler, possible rads upstairs with buffer tank, as we
4. are hoping we wont need a lot of heat in the bedrooms.

5. Yea we had ruled out heat recovery due to the insulation levels not being anywhere near passive standards

1. You need to address the insulation, air-tightness & ventilation. Then run the numbers on what size of heat sysytem you need. Only then can you cost them.
2. Wha?
3. Imo, you've ruled out ufh due to a lack of insulation
4. You're doing a lot of 'hoping' - this is a 5000sqft house! Get this wrong and you're looking at a heating bill the size of a mortgage.
5. You mean you ruled out Mvhr due to a lack of air-tightness?

Cks5

100mm pir insulation then screed on top of that, would prefer to use sand/cement rather than liquid screed.
I had originally thought about raising the door heads to add more floor insulation but that might not be an option now.

I have been researching quite a lot but cant seem to come to a concrete decision on which heat source would be best.

I really would prefer ufh. Would the fact that we wouldn't need as much heat upstairs in bedrooms still not be ok with a heat pump, I understand the lower temperature that any heat pump would heat the radiators to.

How exactly do you get a high degree of airtightness a this stage of the construction ( remember we have bought the house as it stands )
walls, roof, windows and external doors basically.

Condenser

Cks5 wrote: »

100mm pir insulation then screed on top of that, would prefer to use sand/cement rather than liquid screed.
I had originally thought about raising the door heads to add more floor insulation but that might not be an option now.

I have been researching quite a lot but cant seem to come to a concrete decision on which heat source would be best.

I really would prefer ufh. Would the fact that we wouldn't need as much heat upstairs in bedrooms still not be ok with a heat pump, I understand the lower temperature that any heat pump would heat the radiators to.

How exactly do you get a high degree of airtightness a this stage of the construction ( remember we have bought the house as it stands )
walls, roof, windows and external doors basically.

If that's the case then there's no issue using ufh. Using rads with a heat pump will pull down the overall efficiency of the system as the rads require a higher temp and also have no thermal mass. You could get away with fan assisted rads like Smartrads but you'll then need a buffer. If its an option to avoid that I would.
I would use a pumped concrete screed if you can get access to one. Better heat retention than liquid screed and better finish and slightly better heat retention than sand cement.


With airtightness you'll need a sand/cement plaster on your external wall from the very bottom up to hollowcore and from hollowcore to ceiling level upstairs. You'll need a membrane across your upper ceiling and to seal all the joints in the hollowcore, around windows, doors, joints at floors. Basically any point you might think you'll get air ingress and a few you won't think off such as behind sockets etc. Its tedious and expensive to do right. I think in your case bring it to a decent manageable level but going all out will be next to impossible and very expensive.
Once you have it done as well as you can, do a blower door test and see how you're fairing out. You could decide whether HRV was required at this stage. The likes of walltite would help a lot in terms of airtightness but airtightness isn't the end all and be all.

mark_18tp

as cks5 says the house is already built ready for second fix

we can all agree air tightness is important but at this stage the thing is too get it as best as possible.

ufh and radiators this system is best suited to pellet boiler due to the fact of RHI and grants, this system can run with gshp but will be much more expensive.
and well if the boss wants rads you are getting rads lol

pellet boiler with oil back up is the best deal going in my opinion, and will at 5000sq the other important factors are.

zoning heating etc

Cks5

Condenser wrote: »

If that's the case then there's no issue using ufh. Using rads with a heat pump will pull down the overall efficiency of the system as the rads require a higher temp and also have no thermal mass. You could get away with fan assisted rads like Smartrads but you'll then need a buffer. If its an option to avoid that I would.
I would use a pumped concrete screed if you can get access to one. Better heat retention than liquid screed and better finish and slightly better heat retention than sand cement.


With airtightness you'll need a sand/cement plaster on your external wall from the very bottom up to hollowcore and from hollowcore to ceiling level upstairs. You'll need a membrane across your upper ceiling and to seal all the joints in the hollowcore, around windows, doors, joints at floors. Basically any point you might think you'll get air ingress and a few you won't think off such as behind sockets etc. Its tedious and expensive to do right. I think in your case bring it to a decent manageable level but going all out will be next to impossible and very expensive.
Once you have it done as well as you can, do a blower door test and see how you're fairing out. You could decide whether HRV was required at this stage. The likes of walltite would help a lot in terms of airtightness but airtightness isn't the end all and be all.

Exterior walls already plastered
Will look to get a blower test done for sure.
Maybe a silly question but doesn't plastering and skimming the internal block walls create an airtight barrier without the need to tape around windows, doors etc
I di plan to seal around all skirting above and below where it will meet the floor, around internal and external doors, windows etc, is silicone , caulk etc ok for this?
I will make sure the loft hatch is tightly sealed and insulated, also fit sealed chimneys to recessed spots
How do you make airtight behind sockets? Any other tips?
Am I correct in saying that an attic space , if not being lived it, should not be made airtight?

BryanF

Cks5 wrote: »

Exterior walls already plastered
Will look to get a blower test done for sure.

1. Maybe a silly question but doesn't plastering and skimming the internal block walls create an airtight barrier
2. without the need to tape around windows, doors etc
3. I di plan to seal around all skirting above and below where it will meet the floor, around internal and external doors, windows etc,
4. is silicone , caulk etc ok for this?
5. I will make sure the loft hatch is tightly sealed and insulated, also fit sealed chimneys to recessed spots
6. How do you make airtight behind sockets?
7. Any other tips?
8. Am I correct in saying that an attic space , if not being lived it, should not be made airtight?

1. Correct
2. False
3. Is the skirting on? If not its easier to tape/seal the wall/floor junction before skirting goes on
4. Yes but typically tape is used at certain junctions
5. Note sure what you mean by chimneys
6. Is this in a concrete wall? polyfil or plaster etc
7. Deal with Insulation and Ventilation before worrying about heating systems
8. Yes. Assuming the attic is outside of the heated envelope.

Cks5

BryanF wrote: »

1. Correct
2. False
3. Is the skirting on? If not its easier to tape/seal the wall/floor junction before skirting goes on
4. Yes but typically tape is used at certain junctions
5. Note sure what you mean by chimneys
6. Is this in a concrete wall? polyfil or plaster etc
7. Deal with Insulation and Ventilation before worrying about heating systems
8. Yes. Assuming the attic is outside of the heated envelope.

So I should be applying tape around doors, windows, where the floor meets the wall? Where else at this stage in the build?
How about concrete 1st floor taping?
Skirting is not on
6. Yes concrete internal walls
7. Insulation is what it is on the build, I can't increase it anymore without insulating the internal external walls, which I understand can lead to damp problems
Floor looks like a max of 100 pir. And 300mm wool in the loft

I was speaking to someone tonight who is heating a large house of a gshp, built in 2010
Couldn't really get a defining answer to running costs as basically they don't need to look at bills, lucky sods! They had oil as a backup also

mark_18tp

know a couple of my clients run gshp and say there electricity bills are high, considering getting pv in to offset

in all cases of using renewable tech to heat, always put in a backup, such as a oil boiler, just incase of break downs awaiting parts etc.

good luck with the build.

BryanF

Cks5 wrote: »

1. So I should be applying tape around doors, windows, where the floor meets the wall?
2. Where else at this stage in the build?
3. How about concrete 1st floor taping?
Skirting is not on
6. Yes concrete internal walls
7. Insulation is what it is on the build, I can't increase it anymore without insulating the internal external walls,
8. which I understand can lead to damp problems
Floor looks like a max of 100 pir. And 300mm wool in the loft

I was speaking to someone tonight who is heating a large house of a gshp, built in 2010
Couldn't really get a defining answer to running costs as basically they don't need to look at bills, lucky sods! They had oil as a backup also

1. Yes
2. TEST
3. Probably to late, tester might advise
7. You could externally insulate, and assuming a thermal camera shows minimum cold bridges (remainder of 100mm cavity pump bead) dry-lining may a solution worth looking at considering the massive footprint you'll have to heat, and the concrete elsewhere acting as a thermal mass regulator
8. If there are cold bridges. TEST
9. 5000sqft I would increase the loft insulation with careful attention to wall insulation overlap.

Condenser

mark_18tp wrote: »

in all cases of using renewable tech to heat, always put in a backup, such as a oil boiler

Don't do this. Things are expensive enough without doubling up on items.




Get a reputable installer with recommendations and with a proper service back up to fix all elements of the system. You'll get a good cheap system to run and piece of mind if it breaks down. Any installer worth their salt will have parts on hand to fix problems speedily.

mark_18tp

I would like to agree. I have seen it a number of times, gshp and ashp installations and it hitting problems small faults and a part required, takes sometimes a week to get (always the part the agents/suppiler doesn't have), and client left with no heat.

i know its a extra cost, but i would.

galwaytt

mark_18tp wrote: »

I would like to agree. I have seen it a number of times, gshp and ashp installations and it hitting problems small faults and a part required, takes sometimes a week to get (always the part the agents/suppiler doesn't have), and client left with no heat.

i know its a extra cost, but i would.

Correct. Always have a back up.

I have had no space heating since 27th Dec due to a boiler fault, and it's not funny.

Condenser

galwaytt wrote: »

Correct. Always have a back up.

I have had no space heating since 27th Dec due to a boiler fault, and it's not funny.

So are you going to have a boiler to back up your boiler?

Cks5

Condenser wrote: »

So are you going to have a boiler to back up your boiler?

Fair point

Anyone have experience of the pros and cons of having a back boiler linked to a wood burner in a new build

BryanF

Cks5 wrote: »

Fair point

Anyone have experience of the pros and cons of having a back boiler linked to a wood burner in a new build

A definite imo

don't leave the location of your heating systems to chance. Your designer should consider the distance of services ie from boilers to tank to rads/hw taps etc. And air source location for stove.

galwaytt

Condenser wrote: »

So are you going to have a boiler to back up your boiler?

... Doesn't seem so silly right now.....But my buffer tank does have a spare set of connections unused. ...

mark_18tp

lots of ways to have a back up in any heating system, just take it into consideration when at design stage. it all depends on what you install as your primary source of heat and what works along with it and links in with ease.

a gshp and ashp can be a bit tricky to back up with say an oil boiler or back boiler due to the difference in temperature of heating etc, as gshp and ashp operate a lower temperature etc on heating side.

as i say take all in consideration when designing system

gooseygander

Have a stove to light, we are going with ashp and will also have two room sealed stoves with external air supply, one in kitchen/living/dining area and other in the "good" sitting room, if in the event of heating malfunctions surely lighting a stove will tide us over until problems are sorted ?