Room in Roof insulalation

[Steveb21]

I am planning to increase the insulation in my very chilly dormer bungalow.
Loft and Room in Roof.

Current insulation is very patchy and prob not much more than 100mm
Should I remove the old and lay the new? or lay the new on top of the existing?

Removing will be a pain however then the laying will be all nice and equal.
If I lay over the top should I fill in the patches will insulation?

Home base have an offer for:
https://www.homebase.co.uk/knauf-earthwool-loft-roll-200mm_p394101

I was thinking of laying the above x2 - will give me minimum insulation depth of 400m.

 

[foxhole]

I am planning to increase the insulation in my very chilly dormer bungalow.
Loft and Room in Roof.

Current insulation is very patchy and prob not much more than 100mm
Should I remove the old and lay the new? or lay the new on top of the existing?

Removing will be a pain however then the laying will be all nice and equal.
If I lay over the top should I fill in the patches will insulation?

Home base have an offer for:
https://www.homebase.co.uk/knauf-earthwool-loft-roll-200mm_p394101

I was thinking of laying the above x2 - will give me minimum insulation depth of 400m.

Yes fill any voids , bought mine locally via Facebook shop £12 a roll .

 

[Steveb21]

Yes fill any voids , bought mine locally via Facebook shop £12 a roll .

This Homebase deal works out £12.75 a roll which ain’t bad.

Is it possible to have too much Insullation? If I add 400mm and some parts are already 100mm ... il out touching 500m on some areas

 

[foxhole]

This Homebase deal works out £12.75 a roll which ain’t bad.

Is it possible to have too much Insullation? If I add 400mm and some parts are already 100mm ... il out touching 500m on some areas

I have 400mm minimum in mine .

 

[plastic_peanut]

Tackled this recently. The original plan was to remove the original insulation but after starting the job we realised the original insulation was a mixture of a particulate insulation and sheeting.

Opted to keep it and used the Knauf king size space blanket. With it being encapsulated it was easy to unroll and manipulate. More expensive but Infound it saved time overall

 

[Steveb21]

I am still in 2 minds to lift the current insulation, bag and take to local rubbish tip.

The dormer area is a tight fit and whoever laid the insulation has done an awful job - see pics.

 

[Steveb21]

Hoping to start this shortly... still undecided if I should remove the current insulation and start from scratch or lay over it?

If I am correct the original joists are 70mm depth, the joists which are set I assume from the dormer extension are 200m depth.

It appears that the original joist run in the middle(ish) of the new joists (which are spaced approx. 380mm apart). If remove old insulation and lay 200m insulation it would leave a 70mm void on either side of the old joist. Would this be OK or should I look to fill that aswell?!

 

[boringoldcodger]

It appears that the original joist run in the middle(ish) of the new joists (which are spaced approx. 380mm apart). If remove old insulation and lay 200m insulation it would leave a 70mm void on either side of the old joist. Would this be OK or should I look to fill that aswell?!

200mm is the depth, not the width. Your Homebase link says that those rolls are available so that they can be split into 380mm widths.

 

[Steveb21]

200mm is the depth, not the width. Your Homebase link says that those rolls are available so that they can be split into 380mm widths.

Morning, yes however I am not sure I have explained correctly.

70mm Depth Original joist
200mm Depth New joist
The width spacing of the new joists is 380mm

When insulating 200mm I will have to compact it slightly as where the old joist is the total depth (new to original joist) will be 130mm.

 

[IT Minion]

With 200mm joists and another joist 70mm tall you'd only have 130mm above the centre, you could take a knife to the insulation and run a cut part way through the insulation along the middle of the ~380mm strips, that'll let you settle it down the sides and prevent it being heaped up or squished. Squishing it reduces the effectiveness.

I'd remove the old stuff. Arguably very little benefit keeping it and by removing it you get rid of many years of dust at once fell swoop. Ps, buy a dust mask if you don't already have one.

 

[Steveb21]

I plan to lay 2 layers down - of 200mm each. So totalling 400mm.

The crawl space is a bit awkward and it doesn't look very nice up! Not a job im looking forward - especially if I am removing the old insulation!

 

[Steveb21]

See notes in RED which I have added on to this example below.

My plan was to top up insulation (to 400mm) in areas 4 and then 1. Would I notice any real difference to this taking into account there are area's 2 and 3 that need to be insulated as well?

 

[IT Minion]

See notes in RED which I have added on to this example below.

My plan was to top up insulation (to 400mm) in areas 4 and then 1. Would I notice any real difference to this taking into account there are area's 2 and 3 that need to be insulated as well?View attachment 179475

Some, area 1 will stop the eheat from downstairs escape out the roof, so it may become more snug but the upstairs room will still lose a lot through the walls.

 

[Steveb21]

Some, area 1 will stop the eheat from downstairs escape out the roof, so it may become more snug but the upstairs room will still lose a lot through the walls.

Yes. I have a draught coming from some where in the rooms downstairs - in the area's to the side of the dormer so I am assuming/hoping it may be from area 1.

Main objective firstly is to stop heat escaping from downstairs.

 

[Steveb21]

I have noticed on one side of the dormer in the crawl space the end of the joists are exposed (have not checked the other sides as of yet). I assume I am losing vast amounts of heat here as the rooms below have a draughty feeling.

Would Kingspan\Celotex be suitable to fill these area's or can I just push some insulation wool in when I do the rest of the area?

Peeling back some of the insulation on the stud walls the plaster board has a silver backing - I assume this is vapour proof? Should I leave the wool type of insulation here or replace with Kingspan/Celotex?

I would really like to clear it all and start from scratch!