UFH downstairs but nothing upstairs?

[Roz]

Hello, 

 

We're planning on having wet underfloor heating downstairs in our very small barn conversion with extension - coming in around 50 square metres maybe. 

 

A family member has suggested not having the underfloor heating upstairs in order to save money. It's true that we don't like a warm upstairs but is this a bad idea? I know we'd need something in the bathroom. But elsewhere? Will the heat from the ground floor heat the upstairs? The place will be insulated to current building regs standards at U values of 0.3 for the walls in both the existing barn and the extension. The barn and extension will be open plan L shape downstairs. 1 double and 1 single bedroom upstairs, and a bathroom.

 

We'll also have a wood burner downstairs, but used infrequently. Due to space issues I'd rather not have the wood burner flue going through the main bedroom and would rather run it outside, but this will mean we don't get the extra heat from the flue in the bedroom when we do fire it up.

[joe90]

My new build has UFH downstairs and not upstairs, the bathrooms have electric towel radiators and our en suite has electric UFH. I believe we will have adequate heating but our back up is a couple af electric radiators fir the very few days a year an extra bit of heating is required. We also have a wood burner and it raises the heat within the whole house (quite large). Ask me again in a years time.

[PeterW]

1 hour ago, joe90 said:

My new build has UFH downstairs and not upstairs, the bathrooms have electric towel radiators and our en suite has electric UFH. I believe we will have adequate heating but our back up is a couple af electric radiators fir the very few days a year an extra bit of heating is required. We also have a wood burner and it raises the heat within the whole house (quite large). Ask me again in a years time.

 

Pretty much just finishing an identical build with electric UFH in bathroom and ensuite and both with electric towel rails. All this is on one circuit that is controlled by a central time clock. 

[joe90]

1 hour ago, PeterW said:

Pretty much just finishing an identical build with electric UFH in bathroom and ensuite and both with electric towel rails. All this is on one circuit that is controlled by a central time clock. 

 

My two bathrooms are on separate time clocks as the ensuite will be used every day but bathroom for visiting guests only.

[PeterW]

Just now, joe90 said:

 

My two bathrooms are on separate time clocks as the ensuite will be used every day but bathroom for visiting guests only.

 

I suggested this but happy to just use the isolator switches on the boxes in the wardrobe behind the bathroom

[joe90]

Great minds think alike ?

[Guest Alphonsox]

4 hours ago, PeterW said:

 

Pretty much just finishing an identical build with electric UFH in bathroom and ensuite and both with electric towel rails. All this is on one circuit that is controlled by a central time clock. 

 

We've got the same, but in a near passive spec house. The OP has a built to building regs which means a lot more heat leakage, i'm not sure what this would mean regarding upstairs heating recommendations.

[Roz]

Thanks @joe90 @PeterW and @Alphonsox . Joe and Peter are both of your builds passive spec or near also? We don't have enough space in our tiny barn conversion to put in more insulation than getting to U 0.3 for walls.

 

We don't have space for radiators, I want to keep all walls free to keep the small rooms flexible. I feel it's less risk to just put the underfloor heating in upstairs, but we're trying to save money where we can. Although I'm not sure what the cost savings would be to be fair.

 

[joe90]

Yes Roz, mine is near passive and I get your point about space for insulation but insulation works on diminishing returns so if you have half the insulation you get more than half the value. Once insulation gets to a certain level airtightness becomes a major factor are you considering MVHR. (Recover the heat from your rooms and fresh warm air in?).

[PeterW]

@Roz how much space do you have...? Air tightness is equally if not more important as insulation so if you get that right you can reduce the airborne heat losses . What is your proposed wall build up..?

[Roz]

@PeterW It's about 30 square metres on each floor. 

 

So 500mm granite wall rubble filled, then structural engineer has specced 40+15mm insulated kooltherm Kingspan plasterboard, although may try to make this up the 'warm battened' way instead as I read a blog that I think was recommended on here that described this method as better for solid stone walls. 

 

Then the extension (which will be open plan, opening up a wall in the barn) is studs and 125mm mineral wool.

 

 

[Roz]

26 minutes ago, joe90 said:

Yes Roz, mine is near passive and I get your point about space for insulation but insulation works on diminishing returns so if you have half the insulation you get more than half the value. Once insulation gets to a certain level airtightness becomes a major factor are you considering MVHR. (Recover the heat from your rooms and fresh warm air in?).

Hi Joe, I did look into them briefly but felt the size of them would be prohibitive as we have no loft space. Hopefully I haven't made this up as now I'm typing it I'm wondering if that's right...  

[joe90]

I must admit mine is quite large, (oversized unit but cheap on Ebay and I have a large loft) you can get single room versions, someone will be along in a mo to tell you more.

[ProDave]

1 hour ago, Roz said:

Thanks @joe90 @PeterW and @Alphonsox . Joe and Peter are both of your builds passive spec or near also? We don't have enough space in our tiny barn conversion to put in more insulation than getting to U 0.3 for walls.

 

We don't have space for radiators, I want to keep all walls free to keep the small rooms flexible. I feel it's less risk to just put the underfloor heating in upstairs, but we're trying to save money where we can. Although I'm not sure what the cost savings would be to be fair.

 

At those U values you will certainly want close spaced pipes in the UFH and will need to run it hotter than many of us do.

 

Definitely pay a lot of attention to air tightness and in particular, don't accidentally construct a "plasterboard tent" inside your stone building with the gap behind the plasterboard open to cold parts i.e. the loft.

[Triassic]

I'd suggest you fit UFH, it's a straightforward DIY job. I've just installed 250 metres worth of pipe in my new groundfloor slab.

 

You could also install it upstairs using aluminium spreader plated fixed under the floor covering.

 

 

[Roz]

35 minutes ago, ProDave said:

At those U values you will certainly want close spaced pipes in the UFH and will need to run it hotter than many of us do.

 

Definitely pay a lot of attention to air tightness and in particular, don't accidentally construct a "plasterboard tent" inside your stone building with the gap behind the plasterboard open to cold parts i.e. the loft.

 

Hi ProDave. We won't have a loft so it shouldn't have anything like this I hope. Unless I'm misunderstanding you.

 

Do you know anything about how close the pipes should be while we're on the subject? I haven't got around to contacting a company yet but heard Wunda are good for supply, I'm sure I can ask them too so apologies if I'm wasting your time by asking. 

 

 

[ProDave]

You need to start by working out your heat input requirements. @JSHarris has made a wonderful spreadsheet to make this easy, I am sure someone will post a link to it very soon.  From that you can wok out how many watts per square metre your UFH system has to deliver and then you can work out pipe spacing etc.

[PeterW]

@Roz are you taking the roof off and digging up the floor..?

 

if you give your build a big woolly hat and a warm pair of boots then you will mitigate the loss through the walls. Then make it airtight and you are well on the way to reducing heat loss. So if you can increase floor uValue and roof uValue then the 0.3 wall value become less of an issue

 

[Roz]

27 minutes ago, PeterW said:

@Roz are you taking the roof off and digging up the floor..?

 

if you give your build a big woolly hat and a warm pair of boots then you will mitigate the loss through the walls. Then make it airtight and you are well on the way to reducing heat loss. So if you can increase floor uValue and roof uValue then the 0.3 wall value become less of an issue

 

 

It has no roof at present, spec says to put in 65+12.5mm kooltherm plasterboard over/under 100mm mineral wool in the roof. We are digging up the floor but can only go to the base of the walls to avoid underpinning, so that's spec 75mm kingpan. (65mm screed, 500g polythene,  75mm kooltherm, 100mm concrete slab, dpm, sand blinding)

 

Any thoughts warmly received!

[PeterW]

11 minutes ago, Roz said:

 

It has no roof at present, spec says to put in 65+12.5mm kooltherm plasterboard over/under 100mm mineral wool in the roof. We are digging up the floor but can only go to the base of the walls to avoid underpinning, so that's spec 75mm kingpan. (65mm screed, 500g polythene,  75mm kooltherm, 100mm concrete slab, dpm, sand blinding)

 

Any thoughts warmly received!

 

Make the slab structural and get rid of that screed !!! Gives you 140mm kooltherm with 100mm concrete. Massively better performance and quicker as only one wet floor trade. 

 

Roof doesnt make sense either as if you use a 200mm joist then you can get 175mm of mineral wool In there then add 40mm of kooltherm and you are 30% better than the spec already. 

 

Can you post plans...?

[Roz]

5 minutes ago, PeterW said:

 

Make the slab structural and get rid of that screed !!! Gives you 140mm kooltherm with 100mm concrete. Massively better performance and quicker as only one wet floor trade. 

 

Roof doesnt make sense either as if you use a 200mm joist then you can get 175mm of mineral wool In there then add 40mm of kooltherm and you are 30% better than the spec already. 

 

Can you post plans...?

Make the slab structural - what does that mean in relation to what we already have? Do you put the insulation down first followed by the concrete? Perhaps this wasn't specified due to the walls not being underpinned? I can't be sure as know little about this section of the build. 

I think the roof has 122mm rafters planned

 

[PeterW]

Yes just put insulation in first. 

 

Check the roof build up as that can be easily improved. 

[Roz]

7 minutes ago, PeterW said:

Yes just put insulation in first. 

 

Check the roof build up as that can be easily improved. 

Thanks Peter, will do. Does putting extra room between heating pipes and insulation in the form of the thicker concrete slab not create more heat loss into the concrete? As the insulation is further away? Perhaps a stupid question.

[PeterW]

The concrete acts as a big storage heater - what is your expected method of heating..?

[Roz]

 

@PeterW Oil fired combi boiler. We have no mains gas and can't afford a ASHP unfortunately. We'll have a wood burner too but realistically will only use it occasionally. Apparently the oil fired UFH might cause havoc with the SAP values so need to get someone to calculate for us. Can more insulation in the floor and roof counteract this? I'm not sure how SAP values work when you get into the details.