New Roof = Major Humidity/Damp in House

[qwertyuiop1]

Just an update: I'm fairly convinced that the issues are as follows:

- lack of insulation and/or no insulation in some areas of the loft = moisture getting up into the loft + damp feeling in the house

- lack of general ventilation in the house (no trickle vents. I do have one air vent in the downstairs cloakroom but is obviously not big enough to serve the whole of the downstairs let alone anything upstairs)

The duct from the extract fan in the bathroom is fine. So is the gable end and the chimney end so no damp there thankfully.

I am able to close off all the bedrooms and bathroom upstairs as well as the entry points to my kitchen and lounge so I did.

(Bear in mind I usually keep all doors open for the free flow of air and was having to run my dehumidifier downstairs as well as all my furnishings were damp as well since all this started (I dried everything up before doing this). Also bear in mind that I keep the house at around 18-21°).

I have several Govee temperature/humidity readers placed around the house. The downstairs kitchen/lounge/dining were staying steady at around 60-62% RH with the doors closed on the weekend. I cracked open the top windows just a touch while keeping doors closed and RH dropped and stayed at 54% RH all day yesterday. No damp feeling furniture since doing any of this (my furnishings were getting damp within 12-24 hours).

As soon as I would enter the entryway and/or head upstairs it was like entering a different world. It was humid and felt like the outdoors was indoors. Cracking a window hasn't helped. The bedrooms where there is some level of ok insulation feel better than the hall/landing and even bathroom but still not good. It is the hall/landing and bathroom area that had the worst "insulation" or for whatever reason, none at all. I don't have enough humidity/temperature readers to put everywhere in the house but I can "feel" .

I've managed to rope someone in for the insulation which will be tackled the end of this week - clearing the loft of the current stuff and replacing with new. Have some retrofit eaves vent trays which will also be slotted in. Will also be putting a vapour barrier down before the insulation. Some may say this is overboard but is how it is done back home and you don't hear of mould/damp problems.

For now I keep doors closed and run the dehumidifier - in particular in my bedroom at night.
 
I am looking at having trickle vents retrofitted to my windows so I don't accidentally close them in the winter and cause more problems. I would ideally like an MVHR but it's very expensive and would have to open the whole house up to run the ducting. If the trickle vents don't work then I will look into a PIV. FYI I have cavity wall insulation as well so overall ventilation is important.

I largely suspect there is some level of damp coming up from the concrete subfloor on the main floor and the people before me didn't put any DPM down. I have found some very odd stuff that they've done that, at this point, I can only laugh about because I'm not sure who in their right mind would do the things they've done. So this is likely to be contributing (I should invest in a multi purpose moisture reader tbh).

I will see how I get on with that.

 

[Notch7]

There is a problem in the loft but it doesn't seem as bad as in the living space. As I said above the problems in the living space were manageable before the new roof.

I struggle to see how your new roof and your living space have humidity problems are connected

the new roof might alter the air flow in the loft space............but the loft space is not really connected to the living space. If the loft floor is poorly insulated it will make the living space to lose heat faster, but that wont alter the amount of moisture in the air

Are you sure the new roof didnt happen to combine with the weather changing -it has suddenly got colder and also very wet at times

The downstairs kitchen/lounge/dining were staying steady at around 60-62% RH with the doors closed on the weekend.

that is slightly on the high side, RH in a house should be maintained between 40 -60%

but 60% is possible with the weather weve been having

what temperature are you maintaining your central heating at?

I havent seen in the thread what your heating source is: is it radiators, underfloor heating, etc.

 

[qwertyuiop1]

I don't understand the connection either as I know that the living and loft space are separate but it is literally the only thing that changed. So how to explain???? New roof, new membranes (from the old bitumen ones), new soffit vents (after roofers failed to realize that I didn't have any to begin with), new dry ridge (which has been opened that roofers didn't initially do for some reason). That's it. Nothing else changed.

I mentioned I keep the house at around 18-21°. I have rads and combi boiler. No issues or changes there. I doubt any leaks. It can't be from the weather only - I've been in the house for 3 years so know how it typically behaves. It has previously had condensation issues in the living space but was under management. I interestingly now don't have condensation on the windows even when it gets colder (which we've had a few of those nights and days sprinkled in).

 

[foxhole]

Roof has zero effect on humidity in home , sounds like all you concerns are self inflicted .

 

[Murdochcat]

Sounds like you are trying to get information to "throw" at the roofers

 

[Notch7]

I don't understand the connection either as I know that the living and loft space are separate but it is literally the only thing that changed.

but it mightve been a change in weather the coincided with the roof change

You mentioned:

. It has previously had condensation issues in the living space but was under management.

given you previously had condensation issues, does that mean you also had humidity issues?


Im not criticising the points you are making just trying to make sense of it to help.

I interestingly now don't have condensation on the windows even when it gets colder (which we've had a few of those nights and days sprinkled in).

have you made any changes to your house -like altering the heating programme times or thermostats?

reduced condensation on windows means that either the air temp in house is higher or humidity is lower


It is possible the weather conditions at the moment are giving you the feeling things are different and you have associated it with the new roof as it coincides. You might need to monitor it for longer over the next 2-3 months of winter and get more of a feel


The reality is the roof has little impact on the living space, the only thing that will make an impact is the insulation at floor level in the loft.

houses dont generally have a vapour barrier between living space and loft, beyond the ceiling plasterboards. Its possible some vapour could travel from loft to living space if the vapour level was seriously elevated in the loft, but you havent said your loft is getting saturated or suffering condensation

 

[JohnD]

I doubt any leaks.

Where do you think the water is coming from?

 

[qwertyuiop1]

Uuggghhhh I am not trying to gather info to throw at the roofers. I'm trying to figure out WHY after doing this change and only this change, I suddenly have huge issues. I do not know how else to iterate:

- NOTHING has changed except the roof as per above. My lifestyle hasn't changed. Nothing. Nodda. Not sure how else to say "nothing" else has changed. I haven't changed any of the programs from the last 3 years in terms of how I heat the house either - same program. I am repeating this because this doesn't seem to be acknowledged.

- yes there was condensation issues in the house before but I did NOT have damp sofas, bedding, blankets, chairs, clothes, pillows etc. Now I do....it was even worse before putting the soffit vents in - the house became what literally felt like a cesspot. Putting the soffit vents in I suddenly had a very different airflow and circulation in the house but dampness was still a problem. This, along with all the other little experiments leads me to believe that the lack of insulation may be AN issue - cold air coming down through the loft and mixing with an already humid-ish living space with not enough ventilation in the living space to boot.

- as this has been going on for several weeks I'm sure I would have seen the impact of a leak if there was one?

Everyone that I know is at a loss and it seems everyone on here is as well. I came on here in case anyone had any other thoughts.

 

[JohnD]

Was the old roof felted, or open to the tiles?

 

[qwertyuiop1]

Felted. With bitumen. It now has the breathable membrane

 

[qwertyuiop1]

but it mightve been a change in weather the coincided with the roof change

You mentioned:

given you previously had condensation issues, does that mean you also had humidity issues?


Im not criticising the points you are making just trying to make sense of it to help.


have you made any changes to your house -like altering the heating programme times or thermostats?

reduced condensation on windows means that either the air temp in house is higher or humidity is lower


It is possible the weather conditions at the moment are giving you the feeling things are different and you have associated it with the new roof as it coincides. You might need to monitor it for longer over the next 2-3 months of winter and get more of a feel


The reality is the roof has little impact on the living space, the only thing that will make an impact is the insulation at floor level in the loft.

houses dont generally have a vapour barrier between living space and loft, beyond the ceiling plasterboards. Its possible some vapour could travel from loft to living space if the vapour level was seriously elevated in the loft, but you havent said your loft is getting saturated or suffering condensation

Those last 2 paragraphs is where my thinking is heading. The insulation is poor and/or missing and/or randomly topped up in the loft. There are no fire hoods on my downlights either which is in the bathroom directly below. So I know humidity from the house is getting into the loft for sure. It was quite bad up there before the soffit vents and then when some of them were plugged with insulation. It was also bad when the ridge wasn't open. It's been better since these changes but I am not sure it's quite right and will defo need to keep an eye on it.

I'm fixing the insulation at the end of this week - removing everything and replacing with new and with vapour barrier. I am very interested in seeing what happens.

 

[qwertyuiop1]

So. Old insulation has been removed and brand new with vapour barrier installed along with eaves trays. New insulated loft hatch and sealed. Bathroom exhaust which goes up through the loft and out the wall also sealed and although not required, downlights have been given hats and also sealed.

Trickle vents also installed in all windows. It's been a few days now and still humid. As long as I don't live in the house it's fine and the RH drops into the 50s at around 18°. I've contacted someone else to have a deeper look at the roof who agreed that it's not functioning properly and while I couldn't find any damp around the chimney breast in the loft, I do wonder if there's a problem with the flashing and/or really does require more ventilation.

I will keep this thread updated in case someone some day and somewhere is going to have a similar question/issue.

 

[mrrusty]

Lot's of talk here about RH. Some misconception about what it means. It is the ratio of water vapour in the air compared to the maximum the air can carry at that temperature. In a room at 22 degrees and 60% RH the relative humidity will increase as the air cools, until at some point the air reaches the dew point (100%RH) and water vapour starts condensing out.

To identify condensation risk, you need two things - a hygrometer and an infrared surface thermometer.

e.g. from the table the saturated vapour pressure at 20 degrees is 17.54mmHg. So at 60% RH it's actual vapour pressure is 0.6 x 17.54 = 10.52mmHg

10.52mmHg equals the saturated vapour pressure at 12 degrees, so any air at 60% RH and 22 degrees, will start condensing if that air is in contact with a cool surface of 12 degrees or less.

With a hygrometer find out room RH and temp. Calculate the dew point. Zap surfaces with a surface infrared thermometer, identify condensation risk.

Ventilation and insulation need to be understood in context. Imagine an unheated but insulated room allowed to cool to 5 degrees while you are away. The weather changes and it's now 10 degrees and 100% RH outside (it's raining). Open the door, let that outside air in and every surface in that insulated room which is still at 5 degrees, is now wringing wet with condensation because the insulation has kept it cold, and stopped it warming up when the weather changed. In this case, insulation worked against you.

 

[RrogerD]

Do you have suspended ground floors? Do you have a leak under them possibly?
My sister once lifted a board in her lounge after heavy rain and it was a swimming pool beneath. Literally, almost up to the underside of the joists.

 

[qwertyuiop1]

I have concrete subfloors on the ground floor of which i know there is moisture in at least one section. But it isn't enough to be causing damp furnishings by far - only condensation build up on the windows if it gets cold. The house seems to be fine as long as you don't breathe or do anything (i.e. live) in the house.

As I say, it had it's minor condensation issues before the new roof but was otherwise fine and as soon as new roof put on, ka-blam. I know it's all supposed to be separate spaces between roof/loft and living space but there absolutely must be a link otherwise I wouldn't have had this.