Roof condensation

[CXRAndy]

Went up in our loft the other day, droplets of moisture all over the plastic membrane.
Its always been that way in our house afair. Even when we had just 50mm loft insultion it happened, now we have around 300mm, it still happens

If you have good loft ventilation

This must be interstitial moisture and heat bleeding through the insulation.

https://www.google.com/search?q=int...ZgBAKABAcgBCMABAQ&sclient=mobile-gws-wiz-serp

 

[Time Waster]

It you do need a new loft hatch in a 70s house then you'll probably need a bigger hatchback. There's a minimum sized hatch requirement these days. Our old 1900s terraced house needed a big one putting in.

 

[CXRAndy]

I'm not sure there is specific requirements for size other than practical fitment. I know they have to meet part L for heat loss of 0.035

I fitted one of these keylite hatches with ladder

https://www.keyliteroofwindows.com/shop/loft-ladder/

The common sizes for between the roof joists

 

[wiggydiggy]

Update.

Roofers just been, nice guy and gave me some good advice without trying to sign me up to get loads of work done.

For now I am going to add a lot more insulation myself and make sure the hatch is insulated and airtight. For the insulation I have boards down the centre of the loft so should be able to roll it out between the jousts. I'm also going to insulate accross more of the boards themselves as I don't need all the storage space the loft offers. I can still store some things if needed ontop of the insulation, I only have light stuff (empty boxes) in there anyway. He's then suggested to lay some paper down on the insulation and leave it a while to see how much condensation I still get dripped onto it.

Before and after picture of what I want. Brown is the boarding, Black is the hatch, green the existing insulation and blue the new. Yellow is where I could put some light items.

 

[CXRAndy]

Sensible simple 👍

 

[wiggydiggy]

Ok all finished, had to wait a week or so for time when I was free. I've pretty much done what I said but added extra insulation along the entire length of the ceiling under the eaves. The central section (boarded walkway) has been covered as I said though i won't be storing anything directly on top of the insulation now, I may get some lightweight tables in the future to sit over the insulation if I need the storage. I also sealed around the edge of the hatch and glued some insulation board to its underside.

Any difference?

Well I've not noticed any condensation (yet!) but I haven't been running the heating as much, this is because (unsurprisingly) the house now retains its heat a lot better, I have the thermo set to 16c in the evening and I've noticed instead of the heating running on/off pretty regular to maintain that temp it'll run to get to it and then shut off for a lot longer. I need to get a couple of rolls of cheap kitchen towel to lay over the top to try and see if any condensation is still dropping.

Cost? £215ish plus about 7 hrs of my labour.

Thanks to all for the advice esp @CXRAndy

Some pic

Before



After

 

[ColinJ]

I didn't understand that the roof condensation thing was such a big problem. Then today, my sister was driving me past this building...

She asked if I could guess what caused it...

Gas explosion?

Nope - dodgy roof insulation with expanding foam causing condensation which rotted the roof timbers!

YIKES!!!

 

[CXRAndy]

I didn't understand that the roof condensation thing was such a big problem. Then today, my sister was driving me past this building...

View attachment 677624

She asked if I could guess what caused it...

Gas explosion?

Nope - dodgy roof insulation with expanding foam causing condensation which rotted the roof timbers!

YIKES!!!

Folk who have had expanding foam insulation in lofts and walls are struggling to sell.

When the mortgage survey finds out, mortgage is in most cases withdrawn

 

[oldwheels]

Folk who have had expanding foam insulation in lofts and walls are struggling to sell.

When the mortgage survey finds out, mortgage is in most cases withdrawn

I had expanding foam insulation in my exterior walls but it seemed to cause internal damp. The installers had all sorts of excuses but under a Scottish government scheme it was all removed and replaced with polystyrene pellets at no cost to me. This was a Scottish government scheme for OAP’s.

 

[Slick]

I had expanding foam insulation in my exterior walls but it seemed to cause internal damp. The installers had all sorts of excuses but under a Scottish government scheme it was all removed and replaced with polystyrene pellets at no cost to me. This was a Scottish government scheme for OAP’s.

It was a scheme for everyone as I got a huge grant to fix a couple of flats I rented out.

The biggest issue in the west of Scotland is that most of our buildings are finished in some sort of roughcast, which is great when there is a cavity, as the rain water can soak in through the inevitable cracks that appear over time and run down the external leaf, hit the DPC level and out. When you fill the cavity, you form a bridge for that rain water to soak into the internal leaf, causing damp. To be perfectly honest, I didn't want the pellets either, but I wouldn't have got the grant if I didn't let them do it as they needed to hit a target for insulating homes at the time.

 

[ColinJ]

Folk who have had expanding foam insulation in lofts and walls are struggling to sell.

When the mortgage survey finds out, mortgage is in most cases withdrawn

That's what my sister told me. Someone she knows has just failed to get a mortgage for that reason.

 

[simongt]

We have a similar issue in the winter. A 1996 NHBC standard build semi. On th advices of the posts ref. adequate ventilation in the roof space, I think that the glass fibre loft insulation should be left a little short of the eaves to allow air to get in and circulate. Some builders being builders, it doesn't look like this has happened in our loft and the insulation appear to have been shoved into the eaves. If I pulled it back allowing about a 10cm. gap, would this solve the issue - ?

 

[wiggydiggy]

We have a similar issue in the winter. A 1996 NHBC standard build semi. On th advices of the posts ref. adequate ventilation in the roof space, I think that the glass fibre loft insulation should be left a little short of the eaves to allow air to get in and circulate. Some builders being builders, it doesn't look like this has happened in our loft and the insulation appear to have been shoved into the eaves. If I pulled it back allowing about a 10cm. gap, would this solve the issue - ?

There is some advice further up saying that - leave a gap at the edge for ventilation. I was careful to keep a gap at the edges.

Reading the stories about the expanding foam and its ability to block all ventilation I'd (amateur) answer that yes a ventilation gap can help. The loft guy that visited me also said the same.

 

[CXRAndy]

There are vent forms which keep an area at the eaves free from insulation blocking it. See this example below, you can push the insulation right upto the underside. The corrugated shape allows air to enter the roof space

 

[CXRAndy]

If I pulled it back allowing about a 10cm. gap, would this solve the issue - ?

See my post above 👍