1st Floor Insulation Depth

BarneyMc

I'm building a 2 storey house and have used concrete slabs for the 1st floor. I was going to use 1 inch of insulation on the 1st floor to get quicker reaction time from the UFH.

From a practical point of view, would 2 inches be better? This might mean I could bury pipework like central vacum system (2 inch duct) and lagged water pipes all at the same level as the insulation?

What's 'normally' allowed for 1st floor insulation and if using the 2 inch option is there a cheaper option (type of insulation)?

AntrimGlens

Barney,
I went for kingspan 100mm on the ground floor and 75mm on first floor on top of slabs, now in fairness our bedrooms are on ground floor with living area on first floor. Ufh went on top of this with 100mm sand cement screed, with 100mm insulation strip around the perimeter of all rooms. I think the level of concrete mass is nearly as important as reaction time, as i see how much heat our floors retain.

We all walk round in bare feet and the plumber said to me to go with a 10mm stone in the screed to allow for greater heat retention, which i didn't do as floor screed man said it would be harder on his pump, cost more and obviously cost more to buy. Talked to a few people and they felt there was minimal advantage.

I notice that the floors and all rooms are warm within a couple of hours of the heating being turned on during the winter, but the house is never what you could call cold due to solid walls and solid floors.
I never priced anything other than kingspan themafloor and xtratherm, but i'd spend the money on insulation.

rampantbunny

BarneyMc wrote: »

What's 'normally' allowed for 1st floor insulation ..

Mine is specced at 30mm Kooltherm K3 and 70mm screed Barney.

My plumber will cut channels in the insulation to run the pipes in, but there will still be some pipe encroaching into the screed, and therefore they might interfere a bit with the UFH pipes. Nothing to be concerned about I'm told.

BarneyMc

I suppose there's no magic depth for insulation on the first floor but looks like something from 25mm to 75mm. I suppose it comes down to what the plumber needs to bury his pipes just as much as the reaction time for the heat to get into the rooms?

rampantbunny

I'd add another to that list Barney; floor to ceiling heights.
On my build I'm seeing that every inch counts.

Paid a visit to my sisters house a few days back (new build). Her ceilings on both ground and first floor are 8ft 1". Not saying they are too low, but I'd prefer higher myself, so wouldn't be adding to the floor makeup unless there is some real benefit.

hexosan

Mine is 25mm insulation and 50mm hemihydrate screed

BarneyMc

hexosan wrote: »

Mine is 25mm insulation and 50mm hemihydrate screed

Have you had any issues with plumbing or any other pipes protruding?

barryoc1

The thinner the insulation the more heat that will be lost to the concrete slabs below rather than being kept in the screed. I would recommend 50mm at least.

BryanF

What's wrong with heating up the first floor slab. Its thermally broken from the external so the only consideration is the reaction time when the heating is put on. But surely in a new build the heating is set to keep the internal temp constant?

barryoc1

BryanF wrote: »

What's wrong with heating up the first floor slab. Its thermally broken from the external so the only consideration is the reaction time when the heating is put on. But surely in a new build the heating is set to keep the internal temp constant?

The slab is generally lined underneath with battens and then plasterboard, creating as such a suspended ceiling with a void. The heat from the floor above will only heat this void and you wont get the benefit in the rooms at ground floor level. The heat in the slab will find it very hard to make its way back up through the insulation and through the screed to be of benefit to the rooms at first floor level.

If you want to use the concrete slabs as a thermal mass for the rooms at first floor level then dont use any insulation and pour the screed directly on the concrete slabs.

rampantbunny

BryanF wrote: »

What's wrong with heating up the first floor slab. Its thermally broken from the external so the only consideration is the reaction time when the heating is put on. But surely in a new build the heating is set to keep the internal temp constant?

I suppose heating the first floor slab wouldn't be considered wasted heat, but for some could be seen as an unwanted radiator.
The concept of having cooler sleeping areas (cooler than the living areas) is attractive for some (me at least).
This is not the reaction time when turning on the heat, but the ability to isolate the upstairs as much as possible....even if the MHRV (if installed) is going to eventually even temps out.

BarneyMc

Interesting thoughts... has anyone any experiences with or without insulation on the 1st floor slabs?

galwaytt

barryoc1 wrote: »

The slab is generally lined underneath with battens and then plasterboard, creating as such a suspended ceiling with a void. The heat from the floor above will only heat this void and you wont get the benefit in the rooms at ground floor level. The heat in the slab will find it very hard to make its way back up through the insulation and through the screed to be of benefit to the rooms at first floor level.

If you want to use the concrete slabs as a thermal mass for the rooms at first floor level then dont use any insulation and pour the screed directly on the concrete slabs.

It's not thermally broken where the slabs are on the walls.

50 mm might work in a timber house and timber deck, but in a concrete one you need more. Otherwise you're heating the structure first, rooms later. I would be looking at maximising the insulation not minimising it.

barryoc1

galwaytt wrote: »

It's not thermally broken where the slabs are on the walls.

50 mm might work in a timber house and timber deck, but in a concrete one you need more. Otherwise you're heating the structure first, rooms later. I would be looking at maximising the insulation not minimising it.

The slabs are supported on the internal leaf of the wall which should be at room temperature anyway so you wont lose that much heat to these walls from the slab and as such they should help as being another thermal mass to hold the heat and release it slowly.

BarneyMc

Spoke with my plumber and he said 50mm insulation would be fine to bury the piping.

Aeroboard seems to be a lot cheaper than the rest so will likely go with that.

BryanF

BarneyMc wrote: »

Spoke with my plumber and he said 50mm insulation would be fine to bury the piping.

Aeroboard seems to be a lot cheaper than the rest so will likely go with that.

50mm Aeroboard as opposed to 30mm kingspan ?

BarneyMc

BryanF wrote: »

50mm Aeroboard as opposed to 30mm kingspan ?

Well good question. We have had varying answers here from 0mm up to 75mm. Anyway surely what's needed is enough insulation to deliver a decent reaction time for berooms.

My 50mm Aeroboard might be finger in the air stuff but it should:
1. Be relatively cheap
2. Provide enough insulation to provide decent reaction times
3. Provide enough depth for plumbing pipes

ferryman35

We are using 50mm in our build with a 100mm perimeter strip, and a 50mm screed.

Our MHRV system uses an interesting concept - most of the ductwork for the upper floor can be attached to the underside of the concrete slabs, and just drill through the hollowcore where required.

We're thinking of doing at least some of the upstairs plumbing the same way - keeping as much as possible in the ground floor service void.

Don't want to breach any rules, but square section pipe lagging in various depths is available for incorporating pipework in the floor insulation

BarneyMc

ferryman35 wrote: »

We are using 50mm in our build with a 100mm perimeter strip, and a 50mm screed.

Met with the company doing my UFH and this is just as they suggested also.

ferryman35 wrote: »

Our MHRV system uses an interesting concept - most of the ductwork for the upper floor can be attached to the underside of the concrete slabs, and just drill through the hollowcore where required.

Where does the opening where the air comes out/in - the upstairs floor?

ferryman35 wrote: »

Don't want to breach any rules, but square section pipe lagging in various depths is available for incorporating pipework in the floor insulation

This would be mostly for ground floor? Can all sorts of pipework be placed there - electrical, plumbing, etc.?

ferryman35

1. The extraction vents can be located on the floor or low down in the walls, and yo bring the ductwork into the room to accommodate whicheve you choose.

The inlet vents are best located high on the walls or on the ceiling above. Doing it this way facilitates circulation of the air through all the 'layers' in the room. There are documents that make a better job of explaining it than I do! I can send you links if you like. From clarity I'm not connected in any way - in fact I found this out by following up other information I got in this forum!

2. You can use it in any floor level, and most normally it would be used for plumbing. I guess it could be used for cablework too but it would be unusual to be running cables in the floor in a domestic setting?? Also,if you did it I'd reckon that cables would have to be in a conduit (like you have to do with main supply from the meter box) because there is something there about insulation materials causing the cables to degrade over time.