# Forum Home Renovation Heating & Cooling  High wall vents and condenstation

## charli

Hello, 
Im new here and I need help...
I have mould and condensation in our cold south facing bedroom in winter so I had an expert in mould/rising damp come out and quote us on adding 2 high wall vents ( there are 2 aleady)  as he said ventilation will fix the problem...it was over $500.. 
If raising the dew point means making the room warmer then wont adding more vents allow more warm air to escape and make it harder to warm the room???? 
thanks in advance 
DIY newby,
Charli

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## rrobor

Cripes Ill wack as many vents in your wall as you like for that price. To a degree he is correct, I had 2 wall vents in our bedroom and blocked them up and got a bit of a mould issue. I then installed ducted heating and its all fixed. Your bedroom is damp, your bed is damp and you are cold. 2 more vents may help a bit  but at $250 a pop boy thats rich. But its not going to solve your problem, you need to dry the room off and thats with warm air.

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## charli

Yes I thought it was too expensive... We have ducted heating already but its the furtherest point from the unit. We also have floor boards which we are thinking of putting insulation underneath (the expol polystyrene type) and windows are large but covered and cant afford to replace or double glaze atm.... 
We can put vents in ourselves but not sure whether they should open to the outside wall or into the eaves/roof space....

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## Naf

Charli what make and model is your house? i.e. weatherboard, brick veneer etc 
Nathan

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## rrobor

Thinking about this a bit more, I think I understand whats going wrong. If you have central heating that will only work well if your room can vent and suck the damp air from your bedroom. I bet when you go to bed, you close the door. If so I would be tempted to leave the door open to see how that works, if that works I wouldnt stick vents on the wall, I would stick them above the door. I would also block the other two.

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## Naf

Just re read the post a bit better, if you already have 2 vents I don't think another 2 will make much difference unless the original ones are clogged with dust or spiderwebs. 
I took all my vents out, they've all been plastered over and I must say the internal walls look much better and cleaner. 
Nathan

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## rrobor

Yes I think Rod would be best on this. As far as I know vents were there to rid heat in summer, I cant see cold damp air rising and going out those.  All I see is what little heat is in the room is going to vent out. It also may be worth while, if possible, to put a secondary return  in the bedroom

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## Naf

http://www.energysmart.com.au/brochures/draughts.pdf 
bit of info here in regards to wall vents, and other energy saving tips

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## Gravy258

My 1950's BV front bedroom does exactly the same mould thing, its knackered the curtains. We sleep with the door open.
Double glazing only makes it worse.
And vents on the wall, don't do bugger all.
I'm looking at ripping out the plaster and installing insulation and a moisture barrier. This will stop the moisture sticking to the cold walls and windows. Hopefully.

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## rrobor

Gravy258 no sorry  I believe you are incorrect. During an 8 hour sleep the average person expells 1 litre of water so if you have a partner thats double. So its not whats getting in , its what you are adding. So please consider not sealing the outdside. Strangling the Mrs and yourself  will fix it, failing that, figure out how to fix your emissions.

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## Smurf

> Gravy258 no sorry I believe you are incorrect. During an 8 hour sleep the average person expells 1 litre of water so if you have a partner thats double. So its not whats getting in , its what you are adding. So please consider not sealing the outdside. Strangling the Mrs and yourself will fix it, failing that, figure out how to fix your emissions.

  Now I'm having visions of people sleeping with a diving mask on and a hose poked through the window to get rid of their emissions...  :Biggrin:  
I've head lots of situations where people have condensation in the house but never had a problem with it myself. I always leave the bedroom doors open and the windows firmly shut.

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## charli

Naf,
Its a 1970's BV house, and there are 2 vents already and seems theyre doing nothing. I range the guy and he says the heat loss is minimal compared to the ventilation. We leave all doors open at night and window open a little. 
To heat up room were going to have the ducted heating serviced and install expol polystyrene insulation under wooden floorboards which are like ice during winter (no carpet).. 
Im happy to try more vents, willing to give anything a go, our curtains are covered in mould also... oh and going to do job myself... 
Thinking about what little heat we have prob exits out the existing 2 vents (abouve heating duct) and they exit into the eaves/roofspace, whereas the new vents were considering are on the other wall, opposite the doorway.. so heat wold have to move around if it were to exit..... wouldnt it??? Hubby was thinking of another roof whirly to shift some air also...

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## rrobor

Just checked and Rod is not on line as he would be the guy to ask Now Im quite sure they do not fit these things now cos it dont make sense. Hot air rises so any heat you have is going out these vents. Now with the window open cold air will come in fall to the floor and drives the hot air up. Personally Id block these vents and every other in your house and add a bit more oomph  to your ducted heating

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## Gravy258

> Gravy258 no sorry  I believe you are incorrect. During an 8 hour sleep the average person expells 1 litre of water so if you have a partner thats double. So its not whats getting in , its what you are adding. So please consider not sealing the outdside. Strangling the Mrs and yourself  will fix it, failing that, figure out how to fix your emissions.

  Incorrect at ..?
My bedroom has double glazing. This helps the window which faces south, but not the wall around it. 
It had two wall vents also, didn't help so i plastered over them, as they vent straight to the roof and let in shocking heat in summer.
The problem is that its warm inside and cold outside, as its south facing and getting no sun in winter condensation is going to form on the cold walls and windows. If the temperature inside and out was equal they'd be no problem.
On the other side of the bedroom wall is the electric meter, which is basically a big hole in the wall to outside. Insulating this really made a difference on that wall in winter.
So this shows that if all the walls were insulated it would do the trick. 
The house has no moisture wrap. Its too old. 
I'm trying to fix the problem using passive means. Ducted heating would work, as would using the aircon to dehumidify the room.  
The best thing to do Charli for a few bucks is what I have to do every winter morning, get a sqeegee and cloth on the windows and wipe away all the water. I get three litres off some days. This hasn't saved the curtains, but the walls are better.  
The missus drying clothes inside over winter doesn't help, they dry in the lounge, but the moisture seems to gravitate towards the nearby colder bedroom, as it would.

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## rrobor

Ok. correction  the average person expells 1½ litres of water over an 8 hour sleep. sorry.

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## joynz

Consider Dampsorb (water absorbing crystals that are placed in containers). You can get it from Bunnings - they had the best price when I was using it). The dampsorb is placed on a mesh type 'shelf'' in a plastic container attracts the water so it pools at the bottom of the container - and you can toss it every few weeks or days. Put a container in the wardrobe - and maybe one or more everywhere you have a mould issue. 
You can buy special containers where the Dampsorb is sold - but we made our own using icecream containers and a wire or plastic flyscreen mesh 'shelf to hold the dampsorb crystals = with the lids put back on and lots of holes drilled in the lid (or a large hole cut out & covered in mesh) so the water can pass through to the container but parts of clothes etc can't fall into the crystals). 
If you have a look at the commercially available ones you'll see what I mean. The three kilo crystal packs were good value. 
Any warm condensate (from cooking, shower or breathing) will travel to the coldest part of the house it can reach - and the coldest part of that room in general. 
I had a huge probelm with mould even though there were lots of vents. (Old post-war concrete prefab house in Melbourne - the landlord was too cheap to buy a bathroom fan or rangehood!)  
I considered getting a dehumidifier (can hire them too, from memory and may be cheaper to run than the air con (?). Ended up buying a house before I went that far - but the Dampsorb really helped.

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## Bloss

Deal with condensation by understanding the cause(s) and removing them - not by trying to treat the resulting moisture (such as wiping off or using dampsorb etc). 
First go here and read a bit:  Your Home Technical Manual - Home Page 
Condensation is about relative humidity and airflow - and in a house temperature differential between surfaces - usually those exposed to inside and outside air - ie: windows and sometimes walls. 
So you need to ensure that the air is moving and not too moist (if you can), but mainly that the moist warmer air is not able pass over a dry cold surface. For windows the easiest is usually curtains with a pelmets. To cater for summer and winter two rows with a light weight one for summer and heavier weight for winter - both will stop the air flow from floor to ceiling against the window. 
Wall vents are no longer mandated and were a left over from days when the worry was the toxic 'humors' and 'vapours' in enclosed spaces were thought to cause illness! We know better now. They all can be closed off - windows and fans and good airflow design for doors etc are much better ways to move air around - and you can get sufficient air movement without you being able to perceive a 'breeze' (although in summer you might prefer the feel and impact on your skin of that faster airflow). They work poorly for ventilation and loose much heat in winter! 
Walls are harder on southern sides too - again curtains along a whole wall work well in winter - pelmets or floor to ceiling and no more than a 10mm gap at the floor. Or insulate the wall cavity - blow-in rockwool works very well - even if done on the coldest wall only (but best for all walls). Floor insulation might help, but most impact will be warmer moist air meeting the cold wall. Ceiling space MUST be insulated - batts for winter internal heat heading up and out and batts and foil properly installed (they work in different ways) to stop radiant heat from roof space. If it is a problem then plaster wall can be removed and foil and batts properly installed then plaster restored - but that's heroic work even if you can DIY it. 
If you have door closed to sleep then increasing the gap below the door by 10mm by planing off a bit can improve the airflow if you have the ducted heating going at night - which I would never do. Heating is generally not needed overnight even in ACT or Melbourne - your clothing and bedding should be more than sufficient. Best to have the timer bring it on so you get up to a warming house saves energy, sleeping will usually be improved (bodies need cooler air to work correctly) and save you money too.  :2thumbsup:  
Plenty of simple things to do - adding wall vents are not one of them!  :Frown:

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## charli

Bloss, "blow-in rockwool works very well ".. Do most insulation people do this? How do they get around the studs? 
Wondering if this will make the room noticeably warmer?

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## Bloss

> Bloss, "blow-in rockwool works very well ".. Do most insulation people do this? How do they get around the studs? 
> Wondering if this will make the room noticeably warmer?

  Sorry haven't been back for a while. Some insulation companies do all types and there are some who specialise in the blow in rockwool. It is used as it is designed especially for wall cavity use. 
The rockwool is placed using a a 'pump' and goes in from above although sometimes from below too. It fills the whole cavity from the back of the internal lining sheet to the brickwork and depending on the width of the cavity can take the R-value to be from R-3 to R-4 - most are around R3.5. My own house had a wider cavity than usual for some reason and that took more fill, and is now over R4 - noticeable improvement in summer and especially winter. 
The installers will drill holes through bricks in areas that are not accessible from above or below - for example under windows. They drill quite small holes in the mortar joins and blow the material through small nozzles then patch the holes. The good operators I have seen (in ACT) do a great job. Experience and years in business count rather than a price cut from a newbie! The fill is hydrophobic so no issues with breaching the cavity. 
See http://www.heat.net.au/action-advice...lation_web.pdf and heres' a sheet for Victoria: http://www.sustainability.vic.gov.au...stallation.pdf

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## charli

Thanks Bloss, got someone out for a quote for the rockwool wall fill and pretty excited about warming up those walls, I have a feeling it will make a big difference.
Failing that we are considering replacing the old huge aluminium glass windows with thick or double glazed windows to update the place too.... I know its an expensive reno but the windows cover such a large part of the walls its no wonder were losing so much heat.  We might even make one window smaller given it takes up such a large portion of our wall....

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## Bloss

> Thanks Bloss, got someone out for a quote for the rockwool wall fill and pretty excited about warming up those walls, I have a feeling it will make a big difference.
> Failing that we are considering replacing the old huge aluminium glass windows with thick or double glazed windows to update the place too.... I know its an expensive reno but the windows cover such a large part of the walls its no wonder were losing so much heat.  We might even make one window smaller given it takes up such a large portion of our wall....

  Best option for the windows is to install _heavy double (or triple) thermal lined curtains_ floor (no more than 10mm gap) to pelmet . If you have sufficient room plan to have the tracks run long enough for the curtains to go past the window ends so that when you need sun and light you can get all you want. In summer and winter the curtains allow flexibility and in winter at night especially are very effective barriers to thermal loss from the room. The idea is to not allow room air to flow over the cold glass surface - basically by creating a still air space between the glass and the curtains. 
In fact that is the first thing you should do _before_ you insulate walls as proper curtains are about 40%-50% better than a single glazed window at reducing thermal loss. Double glazing (with the curtains) can improve that by 10-15%, but at significantly higher cost - justified in very cold climates, but in Oz the alpine areas are about the only place that would be so. 
In Oz the addition of films is more cost effective after the right curtains, but they need to be carefully chosen for the climate and orientation - Australia - Home - Window Films  and Solar Gard Australia and MEP Films by LLumar and Home & Office Products | SunGard Australia

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## charli

> Best option for the windows is to install _heavy double (or triple) thermal lined curtains_ floor (no more than 10mm gap) to pelmet . If you have sufficient room plan to have the tracks run long enough for the curtains to go past the window ends so that when you need sun and light you can get all you want. In summer and winter the curtains allow flexibility and in winter at night especially are very effective barriers to thermal loss from the room. The idea is to not allow room air to flow over the cold glass surface - basically by creating a still air space between the glass and the curtains. 
> In fact that is the first thing you should do _before_ you insulate walls as proper curtains are about 40%-50% better than a single glazed window at reducing thermal loss. Double glazing (with the curtains) can improve that by 10-15%, but at significantly higher cost - justified in very cold climates, but in Oz the alpine areas are about the only place that would be so. 
> In Oz the addition of films is more cost effective after the right curtains, but they need to be carefully chosen for the climate and orientation - Australia - Home - Window Films and Solar Gard Australia and MEP Films by LLumar and Home & Office Products | SunGard Australia

  Thanks for the links might look into that next. Already have thick curtains down to the floor, may have to get ducted heating unit and duct work checked and cleaned also. Stuffed around by wall insulation guys so cant get that done now (didnt want job after quote but forgot to tell me!) Going crazy trying to get this sorted before winter...You have been a great help  :Biggrin:

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## Bloss

> TAlready have thick curtains down to the floor, may have to get ducted heating unit and duct work checked and cleaned also.

  A good 'gap check' is worth doing - run the heater in a cool morning and go along each run of duct is you can and you might be surprised at how much hot air is leaking out. Especially at joins. Of course even new ducting used in Oz is way under-insulated - almost all will feel warm to the touch in operation which means heat is being lost and you are paying to heat the surrounding air! Even little things like wrapping some foil blanket around junctions (which are often just plastic or metal (gal steel) and have no insulation on them at all. Gaffer tape is fine to seal the ducting up.  :2thumbsup:

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## charli

Brilliant, will squeeze myself under the floor when I can to have a look at duct work.... cheers  :Smilie:

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## charli

Just an update on our chronic condensation in the south facing bedrooms, after ignoring the advice for more high wall vents we have since blocked them up and noticed the rooms are much warmer now winter is here.. 
The company we had lined up to do bv wall cavity insulation has partially closed (thanks Peter Garrett) so we didnt get that done but did insulate underneath the floorboards which has made a noticeable difference also..  
We also had the ducted heating cleaned, serviced and fan speed turned up a notch and temp sits between 14-20degrees.  
On colder nights although there is still some "mist" on the windows in the morning it isnt the panes of dripping water it used to be... :2thumbsup:  
Im so happy, I hope it lasts but its looking good!!!

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