Loft Insulation - Dropped Eaves

[DIY TOM]

I have a 1930s semi with condensation issues. I plan to install a PIV unit to help airflow in the house and properly insualte the loft - it hasn't been done in around 40 years and needs insualting and boarding out.

However we have 'Dropped Eaves' (the eaves cut into the ceiling space in the bedrooms below the loft - see pictures) and not sure how to sulate this area.

*That's not my house but it illustrates the feature.

I'm getting cold spots on these areas - it was cold the other night and there was a lot of condensation - you can see on the below picture that it had formed and is dripping down.

I'd like to insulate it, but the space is very narrow so concious I don't want to block up the eaves with insulation and restrict airflow. The below image is looking down the in the loft into the void below. There is only a 100mm gap.

I was advised I can put rockwool down and put aprrox 1m tubes of 50mm waste pipe down there to ensure airflow.

The loft is a 'cold' loft. There is exposed tiles on the loft ceiling so there is airflow from this i'm guessing?

- Has anyone had experience with this type of loft?
- How would you insulate the eaves whilst maintaining airflow?

 

[JohnD]

Slabs of rigid foam boards, cut to size, will slide down there with less risk of gathering at the bottom or getting snagged. This will leave you a better ventilation channel..

The boards are more expensive than mineral wool, but have about twice the insulation as the same thickness of wool, so in your case, are worth it.

If you old lath and plaster ceiling falls down, or you need a new roof, that will be the ideal time to insulate those difficult areas.

 

[DIY TOM]

Thanks for your reply John - I'm not sure i'd get 50mm board insulation down there due it being solid and the gap being as it is. Might be worth a go though.

I've posted this somewhere else and someone suggested using multifoil down the gaps as it will go down easier - but I have never used it before.