Should I completely re-insulate loft?

[melikescheese]

Hi all,

First off - I've read the pinned condensation in loft thread and I reckon that answers my condensation / insulation related questions but have 3 Qs for those more experienced than me! I live in a Victorian terrace and I'm getting issues with condensation damp on my bedroom ceiling and can also see moisture on the inside of the roofing membrane in the loft. The upstairs is also much colder than downstairs and loses heat exceptionally quickly.

Q1 - What material do I even have already / should I replace it?
I know that it is installed wrong in attached pic - should be parallel between joints and perpendicular above them rather than all laid parallel to joists. What is still a bit of a mystery to me is what sort of material it is - most of the insulation material is in silver and orange bags but otherwise unlabelled. Some is just dumped loose.

a) What is it?
b) Should it still be in those bags?
c) Is it appropriate for a house of my age? (should I look to replace with a hygroscopic insulation - e.g. wool?)

Q2 - Is this roofing membrane part of the problem?
The bedroom on the other side of the house doesn't have any of the same issues with damp on the slanted parts of the ceiling, not only is the insulation not pushed right up against the eaves but it seems all the roofing membrane is some sort of matte material whereas on the side with the issue there's a lot of what appears to be plastic.

Non-problem side (felt?):

Problem side (some felt, some plastic?):

Q3 - Are the eaves properly ventilated?
There are two ventilation tiles in the actual roof, but I can't tell from the above pic (or one below from outside) where the eaves ventilation is supposed to be.

Would a house of this age typically have ventilated eaves (and if so I guess I need to clean them out) and if not - would more ventilation tiles help?

 

[RandomGrinch]

a) What is it?
b) Should it still be in those bags?

It is Knauf Space Blanket insulation.

It was quite popular a while back, as it was available with a large government discount from Focus!
Yes, it should be in the bag, and should be laid foil side up.
It was a decent product and easy to lay.
I got rid of mine earlier in the year, as some rats had made their home inside the bags!
And yes, rolls should be laid between rafters, and then perpendicularly over the top.
Modern standards ask for around 270 to 300 mm equivalent insulation thickness, and the space blanket probably doesn't get you there currently.

 

[melikescheese]

Thanks for this! Eek - rats in the bags does not sound fun! Given the fun plastic bag it's inside does that mean it is no longer vapour permeable?

Any thoughts on the two different (black vs grey) membranes on the different sides on the roof? Is there something (easy) I can do about the fact somebody has used the plastic membrane at some point or do I need to get a roofer to come up and replace that part of the roof?

 

[RandomGrinch]

Given the fun plastic bag it's inside does that mean it is no longer vapour permeable?

Don't get hung up on the vapour permeability - roofs have been made with impermeable felt and slates for many years.
Breathability is a slightly different issue for dampness in walls, in properties of this age.

The problem with your sloped section of ceiling and the condensation, looks to me to be a lack of insulation over this area.
Condensation forms where moist warm air hits a cool surface.
If the insulation is thinner, or not covering this area, the condensation will preferentially form here.

Insulation will need to fully cover this area, but not at the expense of ventilation!
Eaves vent trays can help you push insulation in to the eaves, without blocking ventilation.

If you can't cover the area sufficiently, you could insulate the ceiling from below.

Alternatively (and as well!), ensure you aren't creating humid air in the house to start with - don't dry clothes on radiators, use extractor fans etc....

 

[melikescheese]

Thanks for the help - I think I'll grab some vent trays, relay the existing insulation properly and get a little extra to get to the new recommended level.

 

[RandomGrinch]

Thanks for the help - I think I'll grab some vent trays, relay the existing insulation properly and get a little extra to get to the new recommended level.

Stick around, others may have some different/better ideas!

 

[elrick88]

Have you considered a dehumidifier? Had one recently and has made a difference in the house re-moisture. I bought some little humidification readers of Amazon (£5) and the average humidity was around 75-80%.

Re-loft, looks like you need more ventilation up there, get some lap vents on both sides and it will help remove the moisture. Do you dry clothes in that room or is it near a non vented bathroom?