Has anyone installed a positive pressure air flow system in an older house to combat condensation and or mildew/mould growth. I know about heating and fans and dehumidifiers but as its a tenanted property I can’t guaranteed they’d be used and have been reccomended this. Anyone got one, live with one? And yes I’m evil as I rent a house blah blah blah. Thanks.

Where is the mildew? If in the bathroom you could simply link an extractor to the light switch.
You can’t beat opening windows though.
Better to fix the cause than to tackle the result.

possibly OT and/or bolleaux – but a roofer said that there was an issue with older houses as there was so much moisture about and older roofing felt doesn’t breath – the fix being some extra air vents in the roof

older roofing felt doesn’t breath

This is true. Roof would have been ventilated at the soffit. I think this is still done but the new membranes are better.

Could be very wrong on this but I would have thought that a system sucking damp air out of the house from the locations where most of it originates (kitchen and bathroom) would be more effective than pressurising your house so that the damp air is forced to find its own way out through gaps. Unless the system was set up perfectly I could see it exacerbating the problem rather than improving it. If you are worried about tennants not using extract fans how about hard wiring them to timers or a timed circuit?

I have had this issue in all of my rental properties.
I always ask for the advice of the LA environmental health as they will come and visit and give impartial effective experienced advise, plus it shows the tenants that you are not fobbing them off. They produce this leaflet which I distribute to tenants.
I have solved condensation by using all of these on their recommendation:

0) Fix all roofs/guttering/pointing etc – as these can induce penetrating damp and mould that can easily confuse with condensation.
1) Trickle vents on all windows and roof/soffit vents if necc.
2) Humidistat controlled fans in bathrooms and kitchens (I am considering heat recovery fans in lounges and some problem bedrooms)
3) User controlled extractor fans in kitchens.
4) provide condensor tumble dryers and ban tenants from drying clothes on rads/indoors. I take photos of this whenever I find it and remind tenants of their obligations.
5) encourage them to open windows, use a squeegee on shaower tiles to remove standing water etc.
6) Advise tenants on their responsibilities with regard to condensation issues due to cooking, showering/bathing drying clothes and breathing out.
7)positive pressure fan (this is the last thing I would do now as I was recomended this by a damp “professional” and they have not proved effective without some or all of the measures above.)

I await flaming from the haterz.

Richie_B the theory is that it takes warm air from the loft and pressurises the house and forces it out. In practise? Dunno. If the tenants ignore the other issues, like closing trickle vents, sellotaping paper over extractor fans, drying clothes everywhere, not turning on the kitchen extractor fans then the positive pressure air fan thing is useless. So my experience is – last resort..

Open the windows, lots.
Try and dry clothes outside whenever you can.
Vent roof and floor spaces lots.

Open the windows, lots.

This is what we do, that and an extractor fan for cooking. House is left most days with half the window vents open all day when we’re at work. With double glazing, if you don’t air the house it just ends up smelling of sweaty socks…

6) Advise tenants on their responsibilities with regard to condensation issues due to cooking, showering/bathing drying clothes and breathing out.

😯

Yup, the more family members in the house, the more condensation you get.

Good advice peeps. I’d lived in the house for two years with no issues but hey ho. The air pressure theory thing sounds turbets to me as well. I reckon clothes are being dried inside and dehumidifier not used. Toys19 I shall get othat leaflet. Had local EA round for last lot in the house who claimed it was full of damp. He cleared it and noted wet clothes on every radiator and all windows shut:O
House is in good condition apart from the tenats! Condenser tumble dryer will be looked into tomorrow. Thanks chaps.

Ive thought about posting a similar thread in the past. I have an old stone house. Some corners of rooms have mold growing in them.

It got worse 3 years ago roughly when I doubled the loft insulation. The house is now warmer, but will this be making the damp/mold worse?

possibly you increased the temp differentials – now the ‘cold’ (thermal mass) corners attract more than fair share of the humidity.

That’s then possibly exacerbated again by the warmer and more even indoor temp gradients – allowing air to typically hold more moisture.. Real challenge getting right in older properties!

Cold bridging effect seen on otherwise well insulated retro fits – you can often see patterns from it!

Edit: Of course you could just have kids drying towels on rads though 🙂

We have one. We moved in to a new old house in August, and very quickly found it suffered from condensation, damp smells in the bathroom, and black spots on all the walls appearing overnight.

Had the fan fitted, and overnight the condensation on the windows in the bedrooms disappeared. Very very infrequent black spots in the corner of one room now, even over the very wet winter.

We have two small kids so there is constant wet washing drying in front of the stove, and the house seems fine.

The bedrooms have very tight fitting doors, if these are closed, essentially sealing them off from the pressurised stairwell, they will have small amounts of condensation on the windows in the morning. Leave the door open a tiny amount and there is none.

At the same time we had an always-on humidistat boosted fan fitted in the bathroom, that now has no damp smells at all.

Downsides – there is a constant sound of moving air in the stairwell, but it’s not loud and you get used to it. The stairs are also much colder than the rest of the house over the winter as cold loft air is pumped down. Having the fan supplied and fitted was expensive, you can buy them much cheaper online and if you’re happy cutting a hole in the right place, it’s an easy DIY job – my sister also has one fitted for the same reason, with similar results. They apparently don’t use too much power, I’ve not measured how much directly.

I tried turning the fan speed right down to reduce noise and the cold stairs, the damp came back, turning it back up again and it went away again, so it looks like it works.

Take from that what you will – it’s worked for us, it may work for you. Ours came with a 30 day money back satisfaction guarantee which we didn’t need.

Oh, and our loft is well sealed and insulated, we have a few felt vents fitted to allow the air flow for the fan, they seem to do the job.

I’ve got a 100 year old slate roof plenty of ventilation there.

Hurray tenant said she cleaned down affected area 3 weeks ago and problem has not come back. She also had all the windows open in yesterdays sunny weather. Admitted she is not much of a gardener so I’m gravelling over the small lawn for her. This was after she said it was the best rented house she has ever lived in and wants to stay for minimum of two years. Hurray for me and her. May reoccur in winter but for now all is well. Ta for the help anyway.

Screwfix have a 12litre dehumidifier with £40 off right now. Same one I’ve got…..

We’ve got an old house, 1908. Condensation problems no end. Extractors fitted and used in bathroom and kitchen. Bathroom window always open, small amount. No double glazing, we’re in a conservation area and the planning and conservation officer won’t allow us to change the doors and windows. Ironically the windows are 1980s softwood replacements that in no way resemble the original windows.

All of the windows are covered, in fact pouring with condensation, every morning. We don’t open bedroom windows over night, the house just becomes too cold, but spring and autumn with the windows open they are no better. We even have condensation in the summer!

The loft was reinsulated 12 months ago. The house is noticeably warmer. We were due to have the cavity walls insulated but the construction won’t allow it. There would be empty pockets where the foam would reach, thus making cold spots in various places. When I lift the loft hatch the air temp in the loft frigid in the winter.

We’ve tried using a dehumidifier, did make any difference to be honest. Whether an all sing and dancing one would I don’t know.

All I can see the positive air pressure system doing is pumping in cold air from the loft space. If it’s damp out, and when is it not damp outside in the winter, all it will do is pump cold damp air into the house. Thus increasing your heating bills to warm it back up.

Surprised dehumidifier has done you no good. I was amazed at the amount of water they suck up. Have you tried contacting Local Health Authority to get them round to try and swing planning permission. Or even local councillor, M.P. its amazing how useful they can be sometimes when you poke them. Big up impact on physical, mental health, windows not original etc. Its only an email sent to all local rep’s. CC them all on same one get them to fight for your vote!

All I can see the positive air pressure system doing is pumping in cold air from the loft space. If it’s damp out, and when is it not damp outside in the winter, all it will do is pump cold damp air into the house. Thus increasing your heating bills to warm it back up.

I have looked at a couple and they generally tend to have some form of heat recovery or heat exchange going on depending on what you buy. How this works in real life is of course the question.

We’ve tried using a dehumidifier, did make any difference to be honest

Do you have quite a big property?

Most of the cheaper dehumidifiers are only rated for smaller 2 – 3 bed houses.

Might be that you need to spend more on a higher rated dehumidifier or a dessicant dehumidifier to see the benefit…or run two or more in the property.

I’ve challenged the Conservation Officer over windows, doors, extension, etc. point blank NO. That was including the head of planning, 2 local councillors for my parish, one of which is now the Mayor. The sticking point is that the estate is ranked third in the country as the best Edwardian Social Housing project. You wouldn’t believe the protection the Conservation Officer seems to have from “interested parties” about any works carried out on the estate.

3 bedroom semi. So not big. The dehumidifier was the best but it just didn’t seem to take any moisture out of the air. I could understand a loft based dehumidifier, or an air exchanger of sorts, as long as the air being pumped back in was warm and dry. Otherwise the heating bill would just be horrendous.

We have seen an improvement since we had the log burner installed. Downstairs doesn’t see as much condensation as it did. Upstairs is no different.

Our friend is this:

So much of Britain’s housing stock is past its best and unsuitable for modern lifestyles. In the old days people burned coal in open fires to warm their rooms, which ventilated the house very effectively. I bet most washing got dried outdoors as well, and we did a great deal less washing too.

You wouldn’t believe the protection the Conservation Officer seems to have from “interested parties” about any works carried out on the estate.

This can belegally challenged. there are forums full of advice about this.

So much of Britain’s housing stock is past its best and unsuitable for modern lifestyles. In the old days people burned coal in open fires to warm their rooms, which ventilated the house very effectively. I bet most washing got dried outdoors as well, and we did a great deal less washing too.

I agree. I would happily knock my “beautiful” 1870’s (in a conservation area) house down and build a nice passivehaus in its place.
Conservationism is mental.

I’d much rather live in a Edwardian / Victorian house than anything modern. I really like their design.

Yeah, I used to feel that. But I have sunk 10’s of thousands into mine, its still damp and freezing and expensive to run…

The LA’s Conservation Officer can’t point-blank refuse this, what you really should do is get an accredited Conservation Architect involved.
You’re in the north-west somewhere aren’t you? Anything to do with Port sunlight?

aP.

Northern? How very dare you sir!

Hereford. Bulmers Garden City. Built by the Bulmers family, they of Strongbow fame. Still belongs to the family in part. It’s now run as a housing co-op. It’s complicated.

Some very useful info here.

2) Humidistat controlled fans in bathrooms and kitchens

Any recommendations for makes/models?

I had a pressurised system in a previous house. Zero moule and condensation issues, but as it was a relatively new house (1990s) I wouldn’t expect any really.

possibly OT and/or bolleaux – but a roofer said that there was an issue with older houses as there was so much moisture about and older roofing felt doesn’t breath – the fix being some extra air vents in the roof

We tried this in the current late 60s house which has awful condensation and damp. The ‘fitters’ essentially created a leak which they’ve denied all responsibility for, so my humidity has gone up somewhat…

ANy idea of the pricing on the systems? Might be worth a look for me.

This is a centrifugal rather than axial fan and could suck an orange through a hose pipe. Becuase of that it tends to only run for shorter times as it excchanges the air rather quickly. I have these everywhere.

ebay Manrose CF200H
You can also get the CF400H which could suck a melon through a hose pipe..

How noisy are they toys?

Not quiet, bu not too bad, as centrifugal fans tend to be quieter than axial anyway.
Plus they don’t run for long.