Ventilation / Mould

natnifnolnacs

I'm looking for a bit of house advice. We bought our house about 4 years ago. 4 bed semi-d - early 70's house. The house was pretty much in original condition, so old single glazed windows original attic insulation etc.
One of the first things I did was to insulate the attic.I didn't go nuts or anything, just one layer of earthwool I think it was. I was careful enough doing it and left a gap at the eaves...and in fact never insulated over one of the rooms at all. I have noticed things going mouldy up there if left for too long, so there is obviously something going on up there.

About 2 years ago, we got new windows and back door so the house is now fully double glazed. We also had the central heating system replumbed entirely. Since then, I have noticed mould appearing in a few of the rooms, particularly in the porch. this room was badly sealed and never had a radiator in it so I can understand why.

i know the basic premise - a house needs to breathe. We have sealed it up with better fitting and more efficient windows and doors and made the heating more efficient so there is less ventilation. 2 issues though.
1 - what should I do about the attic issue? Obviously it needs more ventilation - what's the best way to acheive this?
2 - Vents throughout the house. I'm sure I need them and will have to fit them...but will they just make the house freezing again? Is there a particular type that I should go for?

Outkast_IRE

With regards to the attic.
Can you confirm that there are no bathroom extracts emptying into the space ?
If there is not, then i would look at getting a roofer to install a few tile vents or if you have an outside wall up there you could look at a wall vent.

With regards to vents throughout the house, i would reccomend them and you can get ones that are better than bog standard that have acoustic and draft proof qualities. You could also look into positive input ventilation - i have heard some very good things on this and its not as invasive as retrofitting vents in every room .

Lumen

First step is to map out where all of your vents are, and make sure they're not blocked up.

Pay particular attention to bathrooms and rooms with combustion appliances.

Even if the attic problem isn't something stupid/specific (e.g. bathroom venting into that space), when you have warm moist air going into a joist-insulated (cold) attic it's going to condense. Do you have downlighters in the ceilings?

natnifnolnacs

There are currently no vents that I am aware of in the house. Definitely no wall vents.

There is nothing venting from the bathroom to the attic. This is something I will need to look at in the next little whileas the bathroom is suffering from mould growth due to the lack of ventilation.

No downlighters, all very standard lighting.

i'm going to tacklet the vent installation myself, but I guess I want to make sure I'm doing things correctly and not just bodging the job. I'll probably start with a vent in the porch which is the worst affected room. It used to be an external car port effort which was then glazed.

Lumen

OK, well start by reading TDF Part F.

http://www.housing.gov.ie/housing/building-standards/tgd-part-f-ventilation/technical-guidance-document-f-ventilation

You'll need permanent open vents in all rooms with combustion appliances.

After that, priority is bedrooms and then wet rooms.

At least with wet rooms you can open a window ("purge ventilation") as long as you have windows in them.

Assuming you're not going full MHRV, if you want some kind of active ventilation you can either pull fresh air in (PIV) or push stale air out (MEV).

Otherwise you can use passive vents with baffles and/or humidity-sensitive openings. Or passive stack.

Maybe hold off knocking holes in wet rooms until you've decided the right approach, since with MEV you won't need any vents in those rooms.

natnifnolnacs

Much obliged. it's hard to know where to start with stuff like this so thanks for the link.

Turtle42

To stop mould in your attic, you need to stop warm moist air getting up there and condensing. My science is a bit fuzzy here but basically air in the house has a higher pressure and will force itself through tiny holes to get out to the colder areas, where it meets a cold surface, and as warm air also holds more moisture, this then condenses on the colder surface. Insulating your attic makes your house warmer and therfore more moist, and your attic colder. So you need to keep moisture and pressure down in your house by installing vents, which I didn't, but I am vigilant about airing the house out well every day and use my window vents religiously when drying clothes in the house. When I insulated our attic I first went crazy with caulk and builders foam to seal anywhere that warm air can escape to the attic space. You would be surprised at how many places air can get through... not just around plumbing/wiring, but along the tops of stud walls aswell. This is a very important part of the process. I put in a new sealed and insulated attic door aswell. Then ventilate the roof space REALLY well. If there aren't vents at the eaves, put in vents in the roof tiles themselves. I bought them from goodwins and got a roofer from golden pages to put them in for 50 quid. Get a gale blowing up there! And then insulate like crazy... If its flat from wall to wall with no tricky thermal bridge areas this is easy and cheap with fibre glass. Do it really thoroughly and well because wherever you don't, warm air will condense on your ceiling and grow mould. I insulated my cold water tank by making a box out of 100mm rigid foam, and did three layers of fibreglass everywhere. for storage you can get chipboard panels that sit on little legs to keep from squashing your insulation. Its really worth insulating the attic well, it makes the biggest difference for the least cost, effort and distruption.

Use the same principle with your porch. If your house air is wet and warm and your porch is cold and badly ventilated, every time you open the internal door the air will rush out and condense, so ventilate the porch well and make sure your internal door has a good seal to stop cold draughts coming in and warm/wet draughts going out.

listermint

Moist Air hitting a cold surface makes mould.

You can eliminate it by doing these things

- eliminate the moist air

and or

- elminating the cold surface.


Moist air sources - You, your breath - sleeping, showers and bath areas, Wet towels - dryer machines , cooking.

These need to be vented properly or removed entirely if possible.


Cold surfaces, - insulation to bring these surfaces up in tempreture would prevent moist air condensing on them. external insulation attic insulation (installed correctly) etc.

mloc123

Outkast_IRE wrote: »

With regards to the attic.
Can you confirm that there are no bathroom extracts emptying into the space ?
If there is not, then i would look at getting a roofer to install a few tile vents or if you have an outside wall up there you could look at a wall vent.

With regards to vents throughout the house, i would reccomend them and you can get ones that are better than bog standard that have acoustic and draft proof qualities. You could also look into positive input ventilation - i have heard some very good things on this and its not as invasive as retrofitting vents in every room .

Any details on draft proof/acoustic vents I have standard hit and miss vents up which I find both noisey and drafty.