Insulating inside roof, ventilation needed???

[ibruceuk]

Hi,

I want to insulate the inside of my roof under the roof tiles so I can board oyut the loft for storage and not have the loft at sub-zero temperatures!

At the moment the house has no ventilation (that I can see), no ridge vents, no soffit vents etc.

Am I correct in assuming I will have to retro fit some kind of ventilation? If so, how many of the circular soffit vents, and how many ridge vents?

It's a 1960's semi.

Cheers,

Ian

 

[ibruceuk]

Anybody......

 

[Mr Winston]

Hi ibruceuk

yes you should have ventilation - especially as insulating the roof will make condensation more likely.

Soffit vents should => 25000mm2/m (check with the maker of the vents for the capacity of the vents)

Circular vents only provide about 6000mm2/m if installed @ 400mm c/c - you need 4 times this amount so a new vented soffit or overfascia vents would be better/easier to provide the right amount of ventilation.

Ridge vents would need to give 5000mm2/m and should be continuous. If your insulation is sloping up to the ridge board then this definately needs to be continuous other wise the ventilation will only work for the sections with ridge vents at the top and soffit vent at the bottom as each space between the rafters will be separate zones.

 

[markie]

you got to have at least 50 mil air gap between tile/slate and what ever insulation you put in between rafters to cerate airflow, and vents in roof or soffits

 

[Nulty]

I know the thread is old but Im doing the insulating myself now.

I have, 2 hours ago, with 70% of the insulation fitted, realised that i need 50mm ventilation between the sarking and insulation.

Problem.

The rafters are 110mm deep
The insulation is 100mm

I have to pull out the batts, extend the rafter depth by 50mm and re-install the insulation, hopefully, with out doing it too much damage.

Its an old house with big enough eaves so making soffit vents should be easy. The ridge vents im not so clear on. Anyone know how to install those?

Advice.

Check your whether your roof is ventilated or unventilated before you install the insulation! It could cause you a lot of trouble![/b]