Help me resolve this basement condensation nightmare....

[ripperuk]

I never understand why someone would install airbricks now when everyone is trying their best to make their homes more efficient.

I assume it's to keep the place ventilated to avoid issues like rotting and condensation. But don't you think my case it's been overdone?

That's the theory but it doesn't work as the ventilation lets in cold wet air which causes condensation. It also means any heat that you do produce gets sucked right out again, it's like running your heating with your front door wide open.

Yeah, that's what I thought too. But whenever I told anyone, they'd slap me down with the reason being that ventilation is needed to stop condensation.

But rorschach, how have you got around the issue of serious condensation?

[Rorschach]

When the weather is good we ventilate by opening windows etc. When the weather is poor we close the windows and run our dehumidifier.

[ripperuk]

I bet it costs you a lot to run it.

If I may ask you a few questions:

1. How bad was your problem and which room(s) were affected?
2. What kind of dehumidifier (make/model) do you have?
3. What are your electric bills like?

[Rorschach]

I'll have to check the details but it's 250W and we run it 2-3 hours a day so it costs about 10p per day but we only use it for 6 months of the year so actually the costs are very low compared to the hassle and damage any damp would cause.

We had bad condensation in most rooms (on the walls) and mould in several rooms too.

[ripperuk]

Afternoon Rorschach...apologies for the late reply. I had a bit of a disaster - I accidently smashed one of my double-glazed windows and have had to find someone to sort it out...still need to deal with it though.

Rorschach, what have you done with your own house vents and air-bricks? Have you blocked them?

Okay, so here's what I did....For the single-glazed window, I simply shoved a carrier bag into the round vent. For the air bricks, I had some spare kingspan pieces, so i cut them out and stuck them on with strong sealant....I've still left a tiny gap around them for a bit of air circulation. Currently the weather has picked up a little, so I'll have to wait and see how it goes. Just to clarify, I haven't blocked the air bricks on the outside.

The single glazed window though is still sweating condensation, so one option I'm thinking is to get a rigid-clear plastic board to stick on the outside....what do you think?

[Rorschach]

Air bricks on the outside are open to vent the cavity, inside they have been sealed using polystyrene insulation and caulking.

[ripperuk]

Air bricks on the outside are open to vent the cavity, inside they have been sealed using polystyrene insulation and caulking.

Is this for all rooms including air bricks that vent the underfloor joists? Won't this be causing any rot to joists or exacerbating the condensation issue?

[Rorschach]

All rooms but not the airbricks that vent under the floor.

Whether you need to vent under the floor really depends on the construction of the house. If there is ventilation under the floor then there should also be insulation and air sealing to keep the cold air from migrating into the conditioned space of the house.

[ripperuk]

Thanks rorschach. Mine is similar too..i.e. sealed air bricks on the inside for all rooms, but the underfloor airbricks are clear.


I thought I'd give you a bit of an update on the sealed basement airbricks. As I mentioned earlier, I didn't totally seal them as I thought some fresh air would be needed. But this morning, what I've noticed is that there is water/condensation on the actual silicon, but not where there are gaps left. The single window still continues to show lots of condensation. I'm going to put on an acrylic/perspex sheet on the outside of the window to see if this makes a difference as I think it's because the air outside is so moist and cold, that it's having a cooling affect on the glass. Will update you soon.