UFH advice

[richo106]

Hi

 

We are more than likely having a ASHP (maybe oil) to supply our renovated 1960's bungalow. We will be turning it into a house hopefully.

 

We will not be able to achieve passive levels of insulation, the quote we have had is based on meeting current regs

 

Downstairs we will be having a new concrete slab with insulation and screed etc, however the question is we can't decide whether to have UFH upstairs aswell? Upstairs we are planning to have carpet in all the bedrooms and then tiles in the bathroom and ensuite.

 

What are peoples experience with this would they recommend UFH and carpets or just radiators suitable for the lower temps? 

 

They have quote spreader plates for the installation method upstairs, is this the best way to install UFH upstairs? Or are the insulated boards better? What would be the floor make up of installing carpet over UFH? would you lay 22 T&G over the pipes and then carpet on top as normal?

 

Also they have quoted to split the house into 14 different zones, 6 downstairs & 8 upstairs with a thermostat in each room. One manifold upstairs and downstairs....is this normal? or overkill?

 

All help greatly appreciated 

Edited November 12, 2021 by richo106

[joth]

17 minutes ago, richo106 said:

Downstairs we will be having a new concrete slab with insulation and screed etc,

How much insulation are you putting under the screed? If digging out and pouring a new slab it's a relatively tiny price increase to add 50mm or more insulation under it, and will pay for itself fairly quickly. Other insulation could feasibly be added at a later date, but the under floor insulation now is your one and only chance

[richo106]

6 minutes ago, joth said:

How much insulation are you putting under the screed? If digging out and pouring a new slab it's a relatively tiny price increase to add 50mm or more insulation under it, and will pay for itself fairly quickly. Other insulation could feasibly be added at a later date, but the under floor insulation now is your one and only chance

We are planning to have 100mm insulation

[SteamyTea]

17 minutes ago, richo106 said:

We are planning to have 100mm insulation

150mm as the very minimum. 175mm would be better.

This is because the UFH heats the slab to about 35⁰C, so the temperature gradient to the ground is greater than a normal floor, which may only be at 16 to 18⁰C.

I take it that the upstairs is a room/s in roof conversion, as it is currently a bungalow.

If insulated well, you may find you need little heating, so maybe just small radiators.

You may find that you need cooling though. This brings us onto ventilation.

Assuming you are doing a full refurbishment, what have you decided about this aspect of it, you have room for a MVHR unit?

You could just heat the slab downstairs and fit either A2AHPs upstairs that heat and cool, or plumb in some plinth heaters to the ASHP. They could also cool in the summer.

One way to reduce overheating in a room in roof (if this is what you are doing), is to fit PV, this can take out 20% if the sun's energy and turn it into useful electricity.

Edited November 12, 2021 by SteamyTea

[richo106]

21 minutes ago, SteamyTea said:

150mm as the very minimum. 175mm would be better.

This is because the UFH heats the slab to about 35⁰C, so the temperature gradient to the ground is greater than a normal floor, which may only be at 16 to 18⁰C.

I take it that the upstairs is a room/s in roof conversion, as it is currently a bungalow.

If insulated well, you may find you need little heating, so maybe just small radiators.

You may find that you need cooling though. This brings us onto ventilation.

Assuming you are doing a full refurbishment, what have you decided about this aspect of it, you have room for a MVHR unit?

You could just heat the slab downstairs and fit either A2AHPs upstairs that heat and cool, or plumb in some plinth heaters to the ASHP. They could also cool in the summer.

One way to reduce overheating in a room in roof (if this is what you are doing), is to fit PV, this can take out 20% if the sun's energy and turn it into useful electricity.

OK I will mention the 150mm to the builders that's no problem

We hoping to add a full story to turn it into a house so it will have a loft etc

Will this change your thoughts?

 

Thanks again

[TonyT]

Agree with everything above.

 

just watch out, the builders will probably say you don’t need to do that, 100mm will be fine.  Probably cause they can’t be arsed digging out any more.

 

make sure the insulation is sealed together and staggered joins, all joins taped well.

Ask  the builders to explain the thought process if they do only want to put in 100mm, then look at Steamytea’s other posts and see comments backed up with scientific formulae/mathematics.

 

 

[SteamyTea]

42 minutes ago, richo106 said:

OK I will mention the 150mm to the builders that's no problem

Say 200mm to builder, then compromise on 175mm.

Ideally you want to reduce the power losses through the floor to less than current building regs.

And don't let them tell you it is a refurbishment and the standards are lower. The floor is one of single largest heat loss areas there is, not worth skimping on as it is the only place you can add a decent thickness without loosing space.

If you are turning it into a house, then you can, if allowed by planning, add extra height for insulation. Go for a warm roof, not really anymore work.

Have you thought of just rebuilding it as a house, then you have full control of every element.

 

What you want to achieve is a highly insulated, airtight box. Then add in the ventilation and heating. Don't trust a builder as most just don't understand modern building design.

[joe90]

I put 200mm insulation under my slab, no UFH upstairs in bedrooms but electric UFH with electric towel radiators in bathrooms on timers.  Yes bedrooms can be a tad cool in mid winter but the odd plug in radiator is fine (IMO) for that odd occasion. Why so many zones? No insulation between them!. My ground floor is one zone controlled by one room stat in the hallway. Flow within the lounge loop is greater so it’s slightly warmer as this is where we sit in the evening. Although I followed passive ideas mine is not up to passive levels, I concluded the cost of UFH (water) was not justified by the odd occasion it would be used.

[JohnMo]

The guy that did my foundation block work, said I wasting my time insulating the floor and foundations as heat only rose upwards, just couldn't comprehend it went downwards and sideway

[SteamyTea]

1 minute ago, joe90 said:

Although I followed passive ideas mine is not up to passive levels

You do have a very good warm roof as well.

[SteamyTea]

1 minute ago, JohnMo said:

The guy that did my foundation block work, said I wasting my time insulating the floor and foundations as heat only rose upwards, just couldn't comprehend it went downwards and sideway

Does he drink lager?

[JohnMo]

Not sure what he drinks, but talks a by product of food

[SteamyTea]

6 minutes ago, JohnMo said:

Not sure what he drinks, but talks a by product of food

Odd that, I sit in the sun by PZ harbour and sometimes chat to a retired bricky.

He talks shit as well.

[Marvin]

8 minutes ago, SteamyTea said:

Odd that, I sit in the sun by PZ harbour and sometimes chat to a retired bricky.

He talks shit as well.

Lets hope he does not read Buildhub...

[richo106]

Thanks for all the replies 

 

The floor currently has a decent void beneath it so digging out is not an issue fortunately!

I’m not sure my mrs will like the idea of no heating in the bedrooms but I will certainly propose it.

 

regarding the zones I have no idea why there is so many zones, I sent them my plans and that is what they came back with (Warmup)

[joth]

Is it 14 zones, or UFH loops?

Either way, I think part L requires a per-room stat on new builds so it's the default spec for most suppliers. At buildregs levels of energy efficiency, it makes sense to agressively turn off heat in unused rooms, but at near passivhaus levels it's a waste of time as, broadly, the whole house will stabilise to a near equal temperature across rooms anyway. (Yet, the complex controls are technically a requirement anyway on a passivhaus new build)

 

 

Edited November 12, 2021 by joth

[SteamyTea]

Lots of zones means a small minimum volume, so you will need a larger buffer tank.

1 hour ago, richo106 said:

The floor currently has a decent void beneath it so digging out is not an issue fortunately

Then get even more insulation in.

1 hour ago, richo106 said:

I’m not sure my mrs will like the idea of no heating in the bedrooms but I will certainly propose it.

You could put in a basic loop on spreaders and accept the the carpet will insulate it a bit. But if you build it right, the MVHR will help heat it, and you can always fit a heating coil into the MVHR.

 

I gave up heavy drinking after making a bedroom proposal. Dangerous places.