Ground Floor Ceiling Insulation - Block Dormer

iamlegend2008

Hi, Im currently looking at ways to insulate the ground floor ceiling (between joists) of a new block built dormer.

From an energy rating persdpective, the BER assessor says there is no need to insulate between the ground floor and first floor (except for bits where there is no living space on the first floor).

From a sound perspective, I understand that rockwool is good for noise dampening but is twice the price of glass wool.

Im interested in knowing what other people are doing in this area.

Any help would be appreciated.

Thanks.

RKQ

iamlegend2008 wrote: »

From a sound perspective, I understand that rockwool is good for noise dampening but is twice the price of glass wool.

IMO insulate with 100mm thick Rockwool Flexi between joists for Sound and Heat insulation. Check sound rating of Moy fibre glass, to compare both.

Sound is very important and it is worth sound-proofing the floor as much as possible.

Heat insulation is also important as it leaves 1st floor as a separate zone, bedrooms etc aren't heated from below during the day.

Heat is expensive, so only heat the zone you are in / using. Heat rises so insulate ceiling to keep ground floor warmer for longer with less heat - less money!

No6

If sound insulation is an issue rock wooll is better than fibreglass but you'll have to consider impact sound too, if you just have bare floorboards on the joists it will be noisey no matter what you put in, a floating floor over the structural floor will give you far beter sound insulation. Check out Part E of the building regs.

The assessor is right you don't need thermal insualtion in intermediate floors as there is no heat loss between them.

RKQ

No6 wrote: »

The assessor is right you don't need thermal insualtion in intermediate floors as there is no heat loss between them.

No6 is technically correct. This is true for BER rating only.... but heat rises, insulation is cheap in the overall construction costs, so IMO insulate between the joists for sound and heat insulation!

The BER calculations are not perfect, e.g rating on geo-thermal etc. The BER differs from the UK equivalent also. It is our current national standard. It too will improve over time.

Follow you gut instinct.... it won't harm or lessen your BER rating but will help with kids or teenagers running around upstairs.

There are numerous details and techniques for sound proofing timber floor joists. Have a look at them, especially 19mm plasterslabs between joists!

krustytheclown

Can insulation be installed bretween the joists after the plywood floor is down and what about the insulated slab could that be applied to first floor ceiling?

daver123

i need to get rockwoool insulation put between the first floor joists, it looks like we are going to have cut out the ceiling and then re slab and plaster it, i am just wondering has anyone done this before and is it a messy job and would it take long to do 2 ceilings which are both 4 metre x 4 metre in size

BryanF

daver123 wrote: »

i need to get rockwoool insulation put between the first floor joists, it looks like we are going to have cut out the ceiling and then re slab and plaster it, i am just wondering has anyone done this before and is it a messy job and would it take long to do 2 ceilings which are both 4 metre x 4 metre in size

its a two person job putting up sheets of plasterboard, and your first time plastering will be some crack.. dont forget about Vapour barrier/air-tightness membrane taped and sealed ON THE WARM SIDE of the insulation
best of luck

gman2k

You could get rockwool insulation blown into the ceiling cavity, but may be difficult to ensure all areas are covered to a depth of min 100mm.