Attic conversion badly insulated

Mad Benny

Our attic conversion is about six years old. It was badly insulated. On a windy day there are drafts everywhere. Around the windows, doors and ceiling.

Last winter during the snow our roof thawed well before our neighbours.

Here is a photo of the ceiling and one of the storage doors. The wood ceiling has gaps and there is a thin layer of fiberglass insulation to allow ventilation.



Gap in the ceiling where heat escapes.



Gaps around the storage doors

.

Insulation under roof in the storage area. It's the same between wooden ceiling and roof.




We got a builder in and he suggested kingspan insulation board on top of the existing ceiling. He suggested plastering over it.

I would prefer to remove the existing ceiling because I want as much headroom as possible.

My questions are:

Any advice on how thick the insulation board should be? Any particular vendor? Is Kingspan the most suitable for this?

Is there a factory made door with frame that would be air tight that we could install for the storage areas?

BryanF

sounds like lack of air0-tightness is your 1st problem before getting to the insulation levels

imho id take down the timber ceiling and check the insulation( note: you must retain 50mm ventilation space between the insulation and the roofing felt, continuously to the presumed eaves ventilation strips)

You should have about 300mm insulation to meet today's standards, Id try to stick with a material that is breathable like the mineral wool your mentioned if possible, if you cannot achieve this quantity of insulation what about a timber insulation board, fixed below the joists, this might also help solve part of the draught issue.

It might be best to included an air tightness membrane, but beware it'll be tricky to fit everywhere.

from the photos its not clear where the insulation is? but I'd recommend draught striping the door (if the insulation is going down between the joists and meeting the wall insulation) otherwise you need to insulated the walls and back of the door( i'd use the wood insulation board for the back of the door)

also the recessed lights are not helping your draught situation. I'd either remove them and find a surface mounted solution or place a proprietary air-tightness cover behind them.

Peter Sweeney

In a typical attic conversion up to 50% of heat is lost through air gaps, irregardless of the type of insulation used. The problem is the lack of care and attention to detail when the insulation was first installed.

Mad Benny

Thanks Peter. I'm sure that is the case. In my attic room there are gaps in the light fittings and in the ceiling itself. The tongue and groove boards aren't attached properly leaving gaps (see photo above). There is not enough insulation behind them.

The lack of snow on our roof during the winter when other houses were completely covered is evidence of this.

I am thinking of removing the ceiling and putting in Xtratherm Rafterloc. Then 25mm xtratherm/quinn/kingspan board. Then the plasterboard. I read this piece of advice on another thread.

Slig

poorly insulated and drafty are two completely different issues. You could put in 3 times as much insulation into the attic and it would make little or no difference. The heated air inside the attic is escaping much quicker than it will lose its heat through conduction.

Removing the t&g boarding, fitting a thin high performance insulation (polyurethane as opposed to mineral fibre) between the rafters with the required ventilation gap and fitting an air proof membrane to the underside of the rafters and joists followed by 2 layers of plasterboard would be a fairly easy retrofit. You can use mineral or glass fibre insulation between and over joists on the sections of flat ceiling as a larger volume will be required to achieve a reasonable level of insulation.

Poor Uncle Tom

Also there is a lot of heat loss at the spot lights and the attic door is not insulated which will heamourage heat to the crawl space to be vented out.