Have i caused bad condensation?Ways to stop it?

lauren1983

HI everyone.

Ive come to post here because im getting abit worried now!

We bought a old house a year ago and we are renovating it.

Does anyone know if we could have caused bad condensation because we had the house re-pebbledashed?

It was never like this last year and now we have a dehumidifier running all the time but as soon as we turn it off the humidity goes back up to 80%. This morning the windows had condensation on them . We do eveything right with regards to ventilation when cooking ect and have left windows open to try and ventilate.

There are a few more things i think may be causing it but im not sure where to start at tackling the problem. I know these things all add up im just wondering if there is anything specific that sticks out to anyone.

1.We have put chimney balloons up the 2 chimneys
2.We have alot of work still needing doing, meaning 3 rooms with out skirting and carpets.
3,We had some rain get in under the door and it got under the laminate flooring.(2 months ago)
4.We had a leak from the washer (3 months ago)
5, i added more loft insulation.
6, we lowered the staircase ceiling and added about 12 inches of insulation in there.

Sorry to go on. Can anyone advice me please?

ariba10

Will this help?

http://www.harfordsonline.com/downloads/condensation%20info.pdf

iamcornholio

The pebble dashing is unlikely to be contributing, but condensation issues will be due to your use of the property or internal work you are doing.

Any wet trade work (plastering etc) will put excess moisture into the air, and if you have concrete floors and unused/underused rooms then air will not be moving around as it should

Ventilation does not just apply to when cooking/bathing etc and you need to ensure that it goes on 24h/day untill the property/humidity becomes stable after you have finished all the work and settled down properly. You need to avoid any rapid changes of heating or ventilation, and keep everything as constant as possible

It can take months for the property to settle down from excessive moisture

Tucker

The Chimney Balloons are far more likely to be contributing than pebble dashing or the old leaks.

Chimneys are a source or 24 hour ventilation and blocking them off will make a big difference.

80% seems high but it is damp generally at the mo. Mine is usually 40 to 50%. However since the weather went wet and warm it's been 60 to 65% and that's in a relatively new house and with us being humidity conscious.

lauren1983

Thank you to everyone for your replies.
They were all very helpfull and have put my mind at rest and now i know what i have to do.

Thank you again, my husband will be happy to not have to listen to me moan about it now :beer:

David_Aldred

Hi lauren1983,
I think you have answered your own question really in that all of these issues will alter the way the property breathes and consequently the levels of unwanted dampness.

An open chimney flue will provide 2-5 air changes per hour to the room it is in. Stopping this air exchange obviously has consequences in respect of airborne moisture levels.

Insulating the loft makes the air above the insulation colder and more likely to condense if ventilation to the roof void is not similarly improved. Remember 50mm air gap between underside of roof covering and top of insulation to be provided along with eaves / ridger vents to Building Regulation standards.

The affects of rendering a property depend upon wall construction and type of render used. A hard dense cement render to an old property reduces evaporation outwards making the wall wetter and if the pores within the wall contain water instead of air, be that condensation or whatever the wall will be colder and if it is colder more prone to condensation within it such that a downward spiral of dampness can result that is able to be sustained even during more favourable weather. More breathable renders are preferred to older buildings especially with soft / weak substrates.

Rate of drying down for leaks / moisture introduced from construction is about 25mm wall thickness per calender month but hopefully such construction moisture will tend to go outwards if the vapour pressure is higher within the property than it is outside (which it usually is within an occupied property).

Wet solid floors from leaks - especially those that have a damp proof membrane beneath them are very slow to dry down and may take well over a year to do so.

Some of the support measures for condensation are increasing background ventilation with controllable vents to walls or window frames ensuring wall vents are ducted all the way through the wall otherwise you will simply be putting warm moist air into the cavity of a cavity wall which will condense out and cause localised damp / mould.

In addition humidistat controlled extractor fans to kitchen / utility / bathroom again ducted all the way through the wall. Suggest 150mm diameter units which shoudl shift 60 litres of air / second compared to 100mm diameter units that only shift 15 litres of air / second. Fan set to overrun 15 minutes once activiated and set to come on at say 65-70% RH. These are automatic units and are much better than relying on manual units.

If you cannot remember to shut bathroom / kitchen door when cooking / bathing fit self closers to prevent warm moist going to colder areas and condensing out.

Provide a thermostat to boiler that allows minimum temperatures to be set - say 15 deg C so the property is not allowed to become cold for significant periods as condensation is temp related.

If cavity wall insulated check for wet insulation / voids to insulation.

Not a copmplete list by any means but hope this helps, kindest regards David Aldred Independent damp and timber surveyor

Tucker

David

Just a quick question regarding % humidity.

I've two room monitors in the house and have kept tabs on them over the past 10 months or so. Throughout winter the RH was quite low, normally in the 40 to 45% and occasionally 35 to 40%. This was despite the outside RH being as high as 90%.

Over the warmer months it's been higher inside and regularly over 50% and often 60 to 65% when the outside humidity is high.

I just wondered if this was a normal trend, in that the internal RH is often higher due to the warmer overall temperature or is it lower in winter because of the artificial heat created by central heating?

iamcornholio

RH monitoring is useless as a condensation monitor as it has no context for the homeowner ...... it is only relative to room temperature, time of year, and the dewpoint relating to materials within the room - all these factors will combine to determine when moisture will condense on various materials

One property may experience condensation at 80% RH, another at 60%,and RH can be equally high or low in winter or summer

Tucker

I'm not asking about humidity in relation to condensation...... hence I haven't mentioned condensation within the post.

I'm just asking how humidity varies over the seasons and if it's generally higher inside in summer over winter.

David_Aldred

Hi Tucker,
It would be nice to have a simple model that behaved as you describe but in reality there can be dramatic differences hour to hour let alone season to season, especially when the air brought into your home is then altered by temp changes and dehumidification / humidification. Kindest regards, Dave

deconstruction

we had really bad condensation in our house for years after moving into a new house, someone suggested a "lofty fan". Its not cheap but we would try anything at this point, the guy fitting it said that the next monrning we would have zero condensation (yeah yeah yeah i thought).

Windows have been dry ever since.

Google "lofty Home Ventilation System" and you should find some more info (i did try posting a link but it wont let me yet)