Insulating between floors

User567363 · 04-01-2025 09:38PM #1

Dormer bungulo

About 20 years old

There is about 200mm of fibreglass insulation between the ground floor and upstairs this insulation is resting on the ground floors celings

There is about 100mm gap above this insulation

This joists are ventilated at the front and back of the house into the crawl space, the crawl space is obviously not heated and not insulated from the outside

Most of the rooms upstairs have about about 12mm laminate flooring, 5mm underlay and about 20mm plywood under this

So the floors upstars are not really insulated from the outisde

House is fine and easy to keep above 20c,and am using less then 1000l keroseen per year but i am always been frugal...

Is this ventilation essential, or could the 100mm gap be filled with insulation at the ends to keep in more heat

Mellor · 05-01-2025 10:49AM

What's the purpose of the insulation in an internal floor? Upstairs is presumably heated.

Also why is the floor ventilating to an ungrateful space. That’s really allowing heat to escape.

was it always a dormer? Sounds like it was originally a bungalow, and when the attic was converted the thermal envelope wasn’t currently realigned.

User567363 · 05-01-2025 03:58PM

https://www.boards.ie/discussion/comment/123019844#Comment_123019844

Thanks Mellor,

All the house heated, insulation described is on the downstairs celings

It is a self build dormer bungalow, maybe built wrong

How are upstairs floors normally ventilated without exposing then to outside temperature

MicktheMan · 05-01-2025 07:28PM

Ventilation is not required in a void between two heated spaces

Mellor · 05-01-2025 11:28PM

https://www.boards.ie/discussion/comment/123021171#Comment_123021171

Sounds like it’s built incorrectly tbh.

Insulation between two heated spaces will not do much (thermally). Insulation is need at the roof line, or more accurately the perimeter of the unheated space.

Internal floor voids shouldn’t be ventilated.

User567363 · 08-01-2025 09:16PM

https://www.boards.ie/discussion/comment/123023794#Comment_123023794

There is lots of insulation everywhere, also in all the stud walls upstairs

The place is easy to heat

So from reading above it is okay to block the air supply to the space between the celing and first floor

Mellor · 09-01-2025 07:52AM

https://www.boards.ie/discussion/comment/123034929#Comment_123034929

Unless the heating system is zoned with separate zones between the room upstairs, then that insulation is not making any difference. It would be acting as acoustic insulation only rather than thermal insulation.