Humidity Levels

Pinky123 · 07-03-2010 11:28pm #1

Hiya,
Can someone tell me what the recommended levels of humidity are in a standard house or where should I go looking for this type of info???
Thanks

DOCARCH · 08-03-2010 1:49pm

Just found this by accident (for the US but relevant I suppose).

Humans control their body temperature mainly by sweating and shivering. The United States Environmental Protection Agency cites the ASHRAE Standard 55-1992 Thermal Environmental Conditions for Human Occupancy, which recommends keeping relative humidity between 30% and 60%, with below 50% preferred to control dust mites. At high humidity sweating is less effective so we feel hotter; thus the desire to remove humidity from air with air conditioning in the summer. In the winter, heating cold outdoor air can decrease indoor relative humidity levels to below 30%, leading to discomfort such as dry skin and excessive thirst.

d'Oracle · 09-03-2010 2:09pm

Pinky123 wrote: »

Hiya,
Can someone tell me what the recommended levels of humidity are in a standard house or where should I go looking for this type of info???
Thanks

You might find something in TGD part C or F
http://www.environ.ie/en/TGD/

But I'm not sure its something that is defined.

Pinky123 · 09-03-2010 3:28pm

Hiya guys, thanks for yer responses.
I am having some probs with condensation on my windows and have access to humidity monitors. I just need to know what % I need to achieve to eliminate the problem. Will be having a fresh air ventilation system installed in the next couple of weeks.

d'Oracle · 09-03-2010 8:49pm

Pinky123 wrote: »

Hiya guys, thanks for yer responses.
I am having some probs with condensation on my windows and have access to humidity monitors. I just need to know what % I need to achieve to eliminate the problem. Will be having a fresh air ventilation system installed in the next couple of weeks.

Out of my league, and also not really a BER thing.
Sorry.

MicktheMan · 09-03-2010 9:21pm

Pinky123 wrote: »

Hiya guys, thanks for yer responses.
I am having some probs with condensation on my windows and have access to humidity monitors. I just need to know what % I need to achieve to eliminate the problem. Will be having a fresh air ventilation system installed in the next couple of weeks.

What is the heating like in the room(s) with the condensation? Moisture, temperature and rel humitity are all linked.
Is the moist air being extracted at points of generation (kitchen, utility and bathrooms)?
Have you had the house tested for airtightness? if what, how airtight and what type of fresh air ventilation system are you having installed?

Relative humidity levels should generally be around 50 - 60% but will fluctuate especially when a lot of activity is happening (cooking, washing etc).

beyondpassive · 10-03-2010 4:32pm

Background Relative humidity varies hugely in Ireland, not only from day to night but also from the south west to the east.

Humidity is related to temperature, and this becomes important for human comfort which covers a wide range fo temperature/humidity relationships. For instance in high humidity conditions in winter, heating needs to be increased by 2-4 degrees to achieve comfort levels. The biggest issue with humidity is condensation. For every degree you raise temperature the air absorbs about 7% extra moisture. So the heating systems we use put up to 10 litres of moisture a day into the air in the house, however because of the way we build our houses, the internal surfaces never get up to room temperature and can fall below dew point. Dew point at 80% humidity at 20 degrees is a surface of under 14 degrees. Ventilation can help but the hole in the wall vents we use are completely insufficient for our humid climate.

Heat recovery ventilation and passive type cold bridge free detailing are essential for reducing condensation risk and creating comfortable indoor air quality and stable temperature and humidity levels of between 50-60% RH.

Pinky123 · 10-03-2010 11:35pm

Heat recovery ventilation and passive type cold bridge free detailing are essential for reducing condensation risk and creating comfortable indoor air quality and stable temperature and humidity levels of between 50-60% RH.

Beyondpassive,
Thank you so much for your reply, info I was looking for.
We have built an ICF house and it is fairly well insulated. The heat recovery system should be up and running in the next couple of weeks. The Humidity Readers we put around the house were giving a reading of between 40% to 55% (industrial and calibrated units) but we are still getting condensation on a lot of our windows, still not sure if it is a sealing prob with windows.
Thanks again
Pinky

sinnerboy · 10-03-2010 11:57pm

Pinky - to comply with b regs you must have an air permeability test done . Good news is that with that process , using smoke guns and other devices you will locate and therefore by able to rectify most or hopefully all leaks . Your HRV investment will pay off even better for doing that .

In the meantime leave windows open as much as possible to assist drying out

corasam · 26-11-2010 1:44pm

Hello,

Since we bought our house 2 years ago my husband and I have been plagued with sinus and throat problems. I recently purchased a device to read the relative humidity in our home and it seems very high. In our bedroom yesterday the lowest level for 24 hours for 69%, seems to avg around 75 in our room but mid 60s in rest of house. A dehumidifier would address symtom but I'm more interested in addressing the cause.

we have condensation on the windows - they and the rest of house are about 10 years old. We have a draught down the chimney - fitted an air balloon but i still think there's draught coming down. Also we have a garage attached to the house and draught from its roller door. the door between the garage and the house has been well sealed, I suspect the wall between the garage and house could be an issue too. I think the windows are an issue too, they seem draughty also. we have started to reseal them overselves.

We did the cavity wall insulation and attic insulation and upgraded the boiler recently. Also replaced french doors which had a gap. I'm afriad we are throwing money at the wrong issues.

I believe the humidity may be a big factor in our ongoing health issues so my first priority is to address that, but suspect our heating problems are related.

My concern is knowing where to start. How best to determine that? Think we need expert advice but who can we talk to to give full picture and start to address biggest problems first. My fear is we'll spend a fortune replacing the windows and garage door and installing a fire stove, and still have same issues after.

Any advice would be much appreciated.

Thanks

MicktheMan · 26-11-2010 2:21pm

corasam wrote: »

Hello,

Since we bought our house 2 years ago my husband and I have been plagued with sinus and throat problems. I recently purchased a device to read the relative humidity in our home and it seems very high. In our bedroom yesterday the lowest level for 24 hours for 69%, seems to avg around 75 in our room but mid 60s in rest of house. A dehumidifier would address symtom but I'm more interested in addressing the cause.

we have condensation on the windows - they and the rest of house are about 10 years old. We have a draught down the chimney - fitted an air balloon but i still think there's draught coming down. Also we have a garage attached to the house and draught from its roller door. the door between the garage and the house has been well sealed, I suspect the wall between the garage and house could be an issue too. I think the windows are an issue too, they seem draughty also. we have started to reseal them overselves.

We did the cavity wall insulation and attic insulation and upgraded the boiler recently. Also replaced french doors which had a gap. I'm afriad we are throwing money at the wrong issues.

I believe the humidity may be a big factor in our ongoing health issues so my first priority is to address that, but suspect our heating problems are related.

My concern is knowing where to start. How best to determine that? Think we need expert advice but who can we talk to to give full picture and start to address biggest problems first. My fear is we'll spend a fortune replacing the windows and garage door and installing a fire stove, and still have same issues after.

Any advice would be much appreciated.

Thanks

Corasam,

From your post above, it look to me that the actions you have taken todate in your house will make your relative humidity (RH) issue worse rather than better.

Moisture generated in the house needs to be ventilated out of the building and replaced by fresh air. External fresh air is colder than the internal air (in winter). By ventilating the house, the rh of the fresh air drops as it warms up and it is therefore able to take up more moisture and thus the air in the house is kept relatively dry. If there is not enough fresh air being ventilated into the house then there is no mechanism to rid the house of the moisture and therefore problems such as condensation (interstitial), mould (hidden mould) can occur depending on other characteristics of the house (such as insulation detail, thermal bridging ...).

MicktheMan · 26-11-2010 2:29pm

PM sent.

tynka · 11-07-2014 11:29am

Hi can give my advice we bought an old bungalow (built in the 60's) last year we have dry lined and replastered it and put in triple glaze in, vents in all the rooms, we have to still insulate the attic, put in a stove in the open fireplace in the sitting room, there were fireplaces in each of the bedrooms beside each other we closed them. And vents were only put in to the old chimneys a month ago. floors were not re done. we put done silver back floor insutation down and laminate flooring. We put in a fitted wardrobe in the back bedroom. After two months living in the house we found green mould growing first around the windows then in the corner of the wall then in the fitted wardrobe then under the bed on the mattress. bought a meter to read the humidity in the room very high all the time over 60 %. there were alot of big evergreen at the back of the house and some other trees at the side of the house we just got them evergreen cut down. Hopeful it will help because were block sun from the side of the house which had mould. Any advice would be helpful

DIYalot · 27-08-2014 9:51pm

tynka wrote: »

After two months living in the house we found green mould growing first around the windows then in the corner of the wall then in the fitted wardrobe then under the bed on the mattress. bought a meter to read the humidity in the room very high all the time over 60 %.

Bought a 70's built house, gutted it, then insulated the ****e out of it, internally and in the attic we put in rockwool. We had it carpeted throughout and had 4 inch trickle vents in each room, this was 4 years ago. We even got a grant for the work at the time and the BER report thought the house was great. Problem was though we had mould appearing in the master bedroom and I was suffering with monthly sinus infections, it drove me mental.

We removed the carpet from the bedroom and installed wooden floors to aid airflow, we had to chuck a brand new divan base after 18 months because of the mould on it. Heres my experience in dealing with this so far

1. Make sure all your vents are open and unblocked
2. Open a bathroom window when showering, if it is raining outside close the windows and dont dry clothes indoors!
3. Air out the house EVERY DRY DAY, for at least 20 minutes
4. Dont air out the house if it is raining outside -for that you need to buy a dehumidifier and whack it on for an hour or while cooking or showering or drying hair etc. or when getting ready for work
5. ALL OF THE ABOVE POINTS TREAT THE SYMPTOMS BUT NOT THE CAUSE

The cause? there are numerous causes buy mainly you need your house to breathe.

Go up into the attic and look at the felt that is beneath your roof tiles, is it black shiny tarry stuff? if it is then go outside and look at the soffits of your house, can you see any vents in these?

If you have an old house, do it up and think everything is great but ignore the roof then you're gonna be in trouble like me.

Old houses do not have ventilation built into the attic space, why? because they didnt stuff the crap out of them with insulation. You mentioned you havent insulated yet, well maybe all the warm moist air is escaping into your attic and causing issues up there too.

When you heavily insulate a house the attic needs to be able to 'breathe' in order for any warm air to escape and not smother your already smothered house. That black shiny tarry felt does not breathe, the new white permeable stuff does -its called a 'breathable membrane'

What now?

Well just this summer I installed a ridge vent in 50% of my roof, i also installed soffit ventilation in relation to the square footage of my attic space. The attic is a lot more 'airy' now, which means any trapped humid air should be expelled out.

So in addition to that I have just installed a Positive Input Ventilation unit, installed it last weekend. My problem now is that it has been pissing rain all week and humidiity has been high so i dont know if this is working or not.

To summarise, get into the attic, look at cobwebs moving in a breeze or go up during the day and see how much light is penetrating your roof or soffits, if there is none then you need to get ventialtion in the attic otherwhise you are simply smothering yourselves.

1. Look at ridge vents and why they are important
2. Look at soffit vens and why they are important
3. Look at 'air sealing' your roof space
4. Check that your shower and kitchen extractor is vented outside, if they are not then get them venting outside the house immediatley
5. Get an insulated 'loft hatch'

Get fresh air into your attic as much as possible in addition to fresh air inside the house.

There is no silver bullet with this stuff, there are so many factors in the cause, effect and resolution to all of this. if you want any more info i can forward on weblinks etc. to sites i've learned everything from.

MicktheMan · 27-08-2014 10:52pm

tynka wrote: »

Any advice would be helpful

All of the following assumes: 1. there are no active leaks in the house, 2. the house is heated sufficiently and 3. this is mainly a winter problem.

Working backwards, amongst other things, mould needs moisture to thrive.

So where is this moisture coming from? The moisture in internal air condensing on cool surfaces or items generally in the cooler part of the house (north or east facing bedrooms for example).

So where does the internal air get the moisture? Normal activities such as cooking, showering, breathing. Abnormal activities such as drying clothes indoors, leaking pipes, excessive number of indoor plants etc

What determines the amount of moisture in the air? 1.The available moisture. 2.The air temperature. The ability of air to support moisture depends solely on the energy available (i.e. air temperature). The higher the air temperature, the more moisture it can support (this is the "relative" piece of relative humidity). Also the colder the air, the less moisture it can support. Therefore, in winter, the outside air is dryer in real terms than the internal air because of the temperature difference. For example, outside air at 5 degC and 95% RH will be dryer than internal air at 20degC and 60% RH by a factor of nearly 2. This is true even when it is raining but cold outside.

So what has ventilation got to do with all this? In summer, nothing. In winter (or the heating season), appropriate ventilation will continuously replace the internal "wet" air with external "dry" air at an appropriate level. This appropriate level is key. A recent report showed that the "hole in the wall vent" is not good enough to deliver appropriate levels of ventilation in the majority of houses.

In your case you have made several changes which have 1; Increased the internal temperature (and therefore the ability of the air to support more moisture), 2; "sealed" up the house and 3; installed, more than likely, in-effective "hole in the wall" ventilation.

I would advise you to consider investigating upgrading your ventilation system to a Demand Control Ventilation (DCV) system.

MicktheMan · 27-08-2014 11:04pm

DIYalot wrote: »

Bought a 70's built house, gutted it, then insulated the ****e out of it, internally and in the attic we put in rockwool. We had it carpeted throughout and had 4 inch trickle vents in each room, this was 4 years ago. We even got a grant for the work at the time and the BER report thought the house was great. Problem was though we had mould appearing in the master bedroom and I was suffering with monthly sinus infections, it drove me mental.

We removed the carpet from the bedroom and installed wooden floors to aid airflow, we had to chuck a brand new divan base after 18 months because of the mould on it. Heres my experience in dealing with this so far

1. Make sure all your vents are open and unblocked
2. Open a bathroom window when showering, if it is raining outside close the windows and dont dry clothes indoors!
3. Air out the house EVERY DRY DAY, for at least 20 minutes
4. Dont air out the house if it is raining outside -for that you need to buy a dehumidifier and whack it on for an hour or while cooking or showering or drying hair etc. or when getting ready for work
5. ALL OF THE ABOVE POINTS TREAT THE SYMPTOMS BUT NOT THE CAUSE

The cause? there are numerous causes buy mainly you need your house to breathe.

Go up into the attic and look at the felt that is beneath your roof tiles, is it black shiny tarry stuff? if it is then go outside and look at the soffits of your house, can you see any vents in these?

If you have an old house, do it up and think everything is great but ignore the roof then you're gonna be in trouble like me.

Old houses do not have ventilation built into the attic space, why? because they didnt stuff the crap out of them with insulation. You mentioned you havent insulated yet, well maybe all the warm moist air is escaping into your attic and causing issues up there too.

When you heavily insulate a house the attic needs to be able to 'breathe' in order for any warm air to escape and not smother your already smothered house. That black shiny tarry felt does not breathe, the new white permeable stuff does -its called a 'breathable membrane'

What now?

Well just this summer I installed a ridge vent in 50% of my roof, i also installed soffit ventilation in relation to the square footage of my attic space. The attic is a lot more 'airy' now, which means any trapped humid air should be expelled out.

So in addition to that I have just installed a Positive Input Ventilation unit, installed it last weekend. My problem now is that it has been pissing rain all week and humidiity has been high so i dont know if this is working or not.

To summarise, get into the attic, look at cobwebs moving in a breeze or go up during the day and see how much light is penetrating your roof or soffits, if there is none then you need to get ventialtion in the attic otherwhise you are simply smothering yourselves.

1. Look at ridge vents and why they are important
2. Look at soffit vens and why they are important
3. Look at 'air sealing' your roof space
4. Check that your shower and kitchen extractor is vented outside, if they are not then get them venting outside the house immediatley
5. Get an insulated 'loft hatch'

Get fresh air into your attic as much as possible in addition to fresh air inside the house.

There is no silver bullet with this stuff, there are so many factors in the cause, effect and resolution to all of this. if you want any more info i can forward on weblinks etc. to sites i've learned everything from.

You are mixing two completely different phenomena up. The roof ventilation, while very important for the health and integrity of the roof structure, is seperate and distinct from internal relative humidity levels. You are simply mis-informed and this shows the danger of building or renovating by the internet.:)
Btw, I don't know if a PIV system is appropriate in your situation. You may, in fact, make matters worse.

tynka · 28-08-2014 9:17am

MicktheMan wrote: »

You are mixing two completely different phenomena up. The roof ventilation, while very important for the health and integrity of the roof structure, is seperate and distinct from internal relative humidity levels. You are simply mis-informed and this shows the danger of building or renovating by the internet.:)
Btw, I don't know if a PIV system is appropriate in your situation. You may, in fact, make matters worse.

What do u think I need to do?

tynka · 28-08-2014 9:18am

MicktheMan wrote: »

You are mixing two completely different phenomena up. The roof ventilation, while very important for the health and integrity of the roof structure, is seperate and distinct from internal relative humidity levels. You are simply mis-informed and this shows the danger of building or renovating by the internet.:)
Btw, I don't know if a PIV system is appropriate in your situation. You may, in fact, make matters worse.

What do u think I need to do?

tynka · 28-08-2014 9:32am

MicktheMan wrote: »

You are mixing two completely different phenomena up. The roof ventilation, while very important for the health and integrity of the roof structure, is seperate and distinct from internal relative humidity levels. You are simply mis-informed and this shows the danger of building or renovating by the internet.:)
Btw, I don't know if a PIV system is appropriate in your situation. You may, in fact, make matters worse.

What do u think I need to do?

DIYalot · 28-08-2014 10:14am

MicktheMan wrote: »

You are mixing two completely different phenomena up. The roof ventilation, while very important for the health and integrity of the roof structure, is seperate and distinct from internal relative humidity levels. You are simply mis-informed and this shows the danger of building or renovating by the internet.:)
Btw, I don't know if a PIV system is appropriate in your situation. You may, in fact, make matters worse.

Well I'm open to suggestions on this because I'm not entirely convinced myself. PIV units make sense in one way but not in another. The reason I tackled the roof was to get warm air out of it during the night in summer because we were constantly running fans as it was too hot, and also to get 'fresh' air into it to feed the PIV which is supposed to pump fresh air into the house to expel the humid air thus reducing humidity, condensation and mold....llike I said, i only installed that last weekend so the jury is out whether that works.

The thing I dont get is if the PIV is taking air from the attic then this air is unheated and probably containing the same moisture as outside then how does it make sense to 'pump' that into the house to replace already heated or less humid air? especially when its raining outside.

Anyway,

As you say, diagnosing this over the internet may not be the best way but I just dont have the budget to pay for a surveyor or contractor to come in.

I'm open to suggestions, lots of info on this issue is related to U.S. or Canadian climates but there must be hundreds if not thousands of Irish people who insulated their homes in the past few years but are now living with stuffy, moist houses.

MicktheMan · 28-08-2014 11:09am

tynka wrote: »

What do u think I need to do?

As I said:

MicktheMan wrote: »

I would advise you to consider investigating upgrading your ventilation system to a Demand Control Ventilation (DCV) system.

MicktheMan · 28-08-2014 11:23am

DIYalot wrote: »

1. The reason I tackled the roof was to get warm air out of it during the night in summer because we were constantly running fans as it was too hot, and also to get 'fresh' air into it to feed the PIV which is supposed to pump fresh air into the house to expel the humid air thus reducing humidity, condensation and mold....llike I said, i only installed that last weekend so the jury is out whether that works.

2. The thing I dont get is if the PIV is taking air from the attic then this air is unheated and probably containing the same moisture as outside then how does it make sense to 'pump' that into the house to replace already heated or less humid air? especially when its raining outside.

3. As you say, diagnosing this over the internet may not be the best way but I just dont have the budget to pay for a surveyor or contractor to come in.

4. but there must be hundreds if not thousands of Irish people who insulated their homes in the past few years but are now living with stuffy, moist houses.

1. Ventilation has nothing to do with removing internal moisture DURING THE SUMMER. How can it, as the outside air contains as much moisture as the inside air. During the heating season, however, it's a different kettle of fish.
2. Please re-read my reply to TYNKA in post #15.
3. Then, like many people, you will continue to struggle with and put up with mould.
4. Yes there are and I have based part of my business around this very fact.

DIYalot · 28-08-2014 12:20pm

MicktheMan wrote: »

1. Ventilation has nothing to do with removing internal moisture DURING THE SUMMER. How can it, as the outside air contains as much moisture as the inside air. During the heating season, however, it's a different kettle of fish.

Ok maybe I wasnt clear there. I did not install the PIV to remove moisture in summer time. Summer time is not a problem for us regarding moisture levels. The only reason I installed it recently is because it has gotten cooler out and easier to work in the attic plus I only installed the ridge and soffit vents this summer. On top of that it has gotten cooler at night so warm air from the day time was starting to condense on the windows at night, first time i've seen it all summer, well its the end of August so normal I guess.

What I did have a problem with in summer was heat built up during the day wasnt going anywhere at night. We had uncomfortable bedrooms due to
1. The bedroom was south facing so sun hits it all day and heats it up
2. Above that is the souh facing heated roofspace which had poor ventilation
3. inadequate (4 inch trickle) venting internally.
4. Could not sleep with the windows open due to noise levels outside

These issues were concentrated around the bedrooms so sleeping with windows open didnt always suit us. So I increased venting in the attic space to help increase the rate that heat is being expelled out of the attic at night in the summer, using ridge and soffit vents. I know the levels up there are seperate from the living space but I thought it makes sense not to have a heated area on top of the area you are trying to cool? The other reason is to get the fresh air into it for the PIV when that kicks in in winter, if that makes sense.

The same bedrooms are the ones with the mold and condensation issues we had been having in winter. So too hot in summer and too moist in winter.

I dunno, you're probably bouncing your head off a wall reading this at this stage, I'm not surprised you've set up business in this area because I think its a ticking time bomb with all the grants and insulation work that was flying around for a few years. Yeah maybe I'll bite the bullet and get someone to install ventilation units, I'll shop around.

Humidity Levels

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