Will insulation under ground floorboards help with a vinyl floor?

[Gozogozo]

Hi
My house is being extended and an unexpected complete rewire means that the floorboards are all up. We are going from floorboards/ply/ engineered wood to suspended floor/feather edged ply/vinyl.

If the gap between foundations & suspended floor is insulated, will that keep us a bit warmer? Reason tells me that it should, but my builder says that it is unnecessary.

Has anyone had any experience either way? If insulated, do you know what sort?

TIA

I have a floating floor much the same as you describe in my kitchen. When I bought the property the floor had been ruined by leak. Anyway when I replaced the floor which was chipboard , underneath were blue bags about 8ft by 4ft wide of insulation(from memory) The point I am making is yes it does make a big difference. It's a warm room and is quite a size , it's in the north . Round here there are quite a few recent properties that have this type of insulation . Replacing the floor took less than a day and I had no help.
I would go to a big builders merchant and en quire about different options.
I had to lift the bags out because they had a lot of decaying wood from the floor and didn't want to do half a job a cleaned it all out.Interesting times with no kitchen and no floor and living in it. Warm as toast though so definitely worth the extra money for insulation

Your builder is probably thinking of heat loss and return on investment.

Heat loss through floors is less than through walls and ceilings, so start by ensuring your loft insulation, and CWI if you have cavity walls, are done; and that you have dealt with draughts, and insulated all hot pipes, and the hot water cylinder if you have one. This has a very good return on investment.

The people with most to gain from floor insulation are those with bare floorboards in an old house, because cold draughts between the boards are very uncomfortable. People with fully carpeted floors will not notice a difference. Your floor is covered with vinyl, so presumably no draughts.

If you can take up the boards yourself, for example if you already need to replace the floor for some other reason; or if you have access, for example from a cellar, it is worth doing. It will not be economical if you have to pay someone. If you do it, leave the airbricks clear, and pay extra attention to packing the gaps round the edges of the room with insulation.

If you want to calculate the heat loss, so you can compare it to cost, google "whole house boiler sizing baxi" and do the calculation twice. Once with floor insulation and once without. I doubt the figure will be much different.

My mistake, I see now that the boards are up.

So yes, insulate between the joists, and between the wall and the edge joists.

Do not fill the space underneath the joists as it is essential for cold airflow between the airbricks to ventilate the void and keep it dry.

Brush out the airbricks and remove any rubbish from under the floor. Insulate any pipes.

Use Knauf mineral wool rolls as used in lofts. Check the label to see it is treated with Ecose which prevents it shedding irritating dust and fibres. It is brown. I would not use the yellow fibreglass any more.

You can drape garden netting between the joists from above, and staple it into position, to support the mineral wool and prevent it dropping out from between the joists.

Look I wrote a post telling the op I have a floating floor, I then tell her my kitchen is / has insulation under the floor . I then go on to tell her my kitchen is warm that's as in warm. floating suspended floor/ is warm as in better than uninsulated.
You go on with a encyclopedias worth of .....to say what I have already said .

A load of cods

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Bump my dog has bigger strucking paws than yours

Thank you for all very detailed responses; very helpful.
So does this extend to voids below first and second floor and should they be similarly filled?

Further information: mid terrace and externally insulated with new warm deck roof so this is probably dotting T's & crossing I's. However we are un overlooked at the front and have a north wind full on there during the winter.

Also this is our only easy time to do things that minimise our ever increasing energy bills. So looking to do anything reasonable and possible. We will look at solar panels in a year or so, when our finances have recovered from this!

I am semi detached, and with just roof insulation and cavity wall ins plus under floor insulation my house is toast and my bills are Modest.
I live on the coast and it's north

I also like my bones warm

The reason for insulating under a ground floor is that the space underneath is unheated and therefore relatively cold.

If you are upstairs, and the room below is heated, then there is no need to insulate the floor.

Sometimes you may put dense mineral wool batts under an upstairs floor to reduce sound transmission. It is heavier and more solid than the wool used for loft insulation, and more expensive.

Yes the ground is cold and that's why most people live inside houses even and as well as, some even have insulation under their boards. I do, and recommend to anyone including the odd piglet I encounter on my travels{grin]