Ufh first floor insulate or not?

briaineo · 18-07-2020 11:47am #1

Hi

Just a quick one our plumber is giving us two options 50mm insulation under pipes or no insulation?

We have a precast solid slab floor?

It would cost approx 500 extra not to insulate in labour and approx 1150 for the insulation which we would put down.

Found floor has a suspended ceiling.

Thanks

Penn · 18-07-2020 3:45pm

You're better off insulating imo. Otherwise heat is just going to absorbed by the floor and you'll be heating the air voids in the hollowcore slab. It won't cause a problem, but just won't be as efficient. A small bit of insulation under the screed keeps all the heat in the room itself.

Metric Tensor · 18-07-2020 10:03pm

If you have a heat pump and underfloor heating your house will spend all its time at a constant temperature anyway. So the only time the slab and cores will take much heat from the room is the first time you turn the heat on.

After that they'll be the same temperature (give or take) as the rest of the house anyway. So all you're doing with the insulation is ensuring that your ground floor heating keeps them at this constant temperature rather than the upper floor heating.

Total waste of money in my opinion and has only grown in popularity because it makes plumbers lives easier.

Calahonda52 · 19-07-2020 10:43am

Let's look at the science here for a moment in the context of heat loss.
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I am assuming there is a suspended ceiling under the HC which is airtight to the room below.
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So what temperature is that air space going to be once the house heats up and what temperature the underside of the slab will be.
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The higher the difference, the greater the heat loss into the ceiling space until it reaches equilibrium.
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The other place for heat loss in into the inner leaf of the external walls supporting and sitting on the HC, so assuming no IWI on these walls there is little or no heat loss.

muddle84 · 19-07-2020 6:27pm

Check with your UFH manufacturer for their recommendations. Plumber told us it wasn't needed and there was no mention of it in the BER but the UFH & Heat Pump manufactured said it require 25mm minimum under the piping.

Makes perfect sense to me to put it in, you want the UFH heating the room above it not the big concrete slab below it.

Metric Tensor · 19-07-2020 7:35pm

The big concrete slab is always heated regardless of whether you put in insulation or not.

Calahonda52 · 19-07-2020 8:54pm

Metric Tensor wrote: »

The big concrete slab is always heated regardless of whether you put in insulation or not.

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Exactly
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Look up the concept of Decrement Delay, thats 2 D's:D

briaineo · 03-08-2020 9:45am

Hi

Thanks for all the replies, our engineer says he’d be happier if we put in a bit, can’t fit 50mm can do 25mm Or 35mm if available

Kilough · 05-08-2020 2:19pm

This pre-cut low profile insulation system seems handy for laying UFH pipes. Anybody used or able to recommend?

https://www.warmup.co.uk/underfloor-heating/water/total-16

Ufh first floor insulate or not?

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