Discussion on damp, ventilation and insulation in very wet areas

[Hadtocomment]

I am probably moving to a rather old building in a very wet area. Ive been a bit bamboozled by all the different advice and thinking about damp and insulation I have received from experts. I've also been reading around the subject. Mumsnet is so knowledgable I don't know if this is the place to ask but I'm getting quite conflicting advice about insulation versus getting rid of damp. Some experts seem to think breathability is the most important thing and these experts are wanting insulation actually removed for this purpose. This goes against what I've always been taught about getting insulation into attics etc to keep heat in! On the radio I'm constantly hearing the argument for more and more insulation to reduce energy costs and keep heat in. The experts i'm talking to think it is harder to heat a damp home and damp can come from condensation and lack of venting as well as from the outside.

I wondered if any of you know about these issues and what your experience might be and if there are any resources you can point me to which you think are good?

Is it a matter of different areas need different ways of thinking or is there some general principles to be applied? Is this an old house/new house thing or is there just disagreement between experts on this? Thanks!

I would say it is a new house/old house thing.

I have an old house but it's not that you can't insulate it at all, just that other things eg preventing drafts may be more important and when you do insulate you need the right materials to stop trapping water inside.

And yes there is disagreement in that people who sell damp-proof courses want to sell you damp-proof courses so are likely to recommend this.

It’s definitely an old house/new house thing. And given there are centuries of homes with changing construction methods you have to assess what does and doesn’t apply to your particular property.

Heritage House runs a good web page with advice that explains which damp proofing tactics you can use on which type of construction:
www.heritage-house.org/damp-and-condensation/managing-damp-in-old-buildings.html

Who are these 'experts' you're talking to?

What types of insulation does the house have? Loft - unrolled insulation between the floor joists or sprayed insulation on the underside of the roof tiles?

Have the previous occupants done anything daft like vent the bathroom into the loft space?

Cavity wall insulation? Sometimes that goes wrong and causes problems.

Can laundry be dried outside or in a tumble drier, or have the previous occupants been air-drying it indoors?

That webpage sorted my damp problems!

I'd had several different opinions on the damp in my house, all involving either doing something expensive or wandering around with a damp meter. A number mentioned rising damp which the website strongly says is a myth.

I followed the advice on the website, had the plaster changed and the damp is gone. The walls just wanted to be happy.

Me too. Through reading just about everything on heritage homes and examining my house is how I discovered the damp in my walls were caused by 1) an idiot repointing the solid 1823 brick walls with fucking concrete. So, I had it chiseled all out and repointed with lime mortar per the heritage homes advice. And 2) also discovered another source of my damp walls was that my air bricks had been over time obscured by soil level going up behind the box hedging, and as my home predated damp proof courses you have to make sure no dirt/soil builds up against an exterior wall. So the advice was to dig a trench around the walls, fill it with gravel and leave brick lined cubbies around the air bricks. These two simple things fixed the damp walls!
I then per the website, scraped back the flaking damaged plaster that some idiot had tried to fix with poly filla and emulsion white damp proof paint. Had the rooms re plastered with proper lime plaster and then painted with a natural wax based interior paint…and voila! Dry walls with proper breathable plaster and paint.

This is really interesting!

I don't want to derail the thread but what is everyone's opinion on tanking basements in old houses?

I would say that there is a limit to how much you can insulate some old houses. When you do insulate, you ideally use breathable (expensive!) materials and ensure there is still ventilation. E.g. sheep's wool instead of the normal loft insulation. Sometimes you can get away with not using the most breathable materials, but it depends on the house. As a pp said, draught exclusion etc can be more productive, but these houses will often remain tricky/expensive to heat.

Personally I would avoid tanking even in a cellar. Sometimes all you have to do with an old cellar is add a ventilation duct.

Wow this is terrific thank you. It is great to get real experiences. I am pondering the trench and gravel thing so that is fascinating to know it has worked for some.