hamish05
Member
A number of plaster walls in my house have molded vents toward the top.
As I intend to repaint shortly, what are the pro's and cons for leaving them as is, or plastering over them?
The most obvious to me are,
1/ they allow heat to escape in winter.
2/ they reduce condensation on windows in winter.
Does the fact that houses are centrally heated and cooled make these vents redundant? (Melbourne location)
I do not seem to notice any wall vents in newly built houses, why?
dymonite69
Member
These are harken to the days of old fireplaces to prevent the build up of exhaust gases. Close them up.
I have cement rendered internal walls and rendered up 4 internal vents last year. All good so far with no mould or smells appearing. Our house is old (1940s) and I think that just as D69 commented, they were there to ventilate fumes from combustion heaters. We use Reverse Cycle electric heating so have no such fumes to worry about.
hamish05
Member
Guess I knew the answer b4 I asked the question. I have decided to immediately fill the vents (8 total) with no more gaps...easy. Will plaster over when painting later.
Maybe the post will prompt others to do likewise.
Thanks everyone
hamish05
Member
Very pleasing results here, "she who dusts" commented this morning, about there being considerably less dust buildup on our furniture since I filled in the vents. In particular, our highly polished red-gum dining room table, which is positioned directly below 2 vents on a north facing wall.
simplelife
Member
I was about to post the same question about wall vents in a 1955 house (which have a considerable draft coming through them in winter) when I found this thread.
Has anyone had any problems after closing them up? Our house is a weatherboard, which we plan to reclad with hardiplank (+ wall insulation) in the near future.
Will we be inviting termites to come party by reducing the airflow within the walls?
cava
Member
One downside to closing ventilation vents, is that in our particular case, my wife has started to open the windows more for fresh air.
Apparently, despite my protestations, she requires fresh air otherwise the gassing off of various furnitures/curtains/carpets etc affects her health. Indoor air quality is a big thing that not too many are aware of.
simplelife
Member
Has anyone else had any experience with filling in plaster vents?
jhamill
Member
i've had 2 vents plastered over in one bedroom (about 3-4 years ago, no noticeable issues). In the other rooms i've covered them with plastic sheets (about 1 year ago). Again no issues, possibly noticeably warmer 
in summer I noticed a lack of warm air blowing in which was the main aim.
simplelife
Member
jhamill thanks. Will get them all plastered over then before summer. Hopefully that will improve our summer suffering!
peter69_56
Member
I had a house built in 70's Brick veneer with small wood heater. Each room had vents. I took out the heater and sealed up the vents. Only down side was I found there was some mould up near the ceilings due to lower air circulation. Also added 100% curtain block on my curtains with pelmut boxes to reduce heat loss. Once again it created some mould inside the window area due to lack of air flow. Its a hard balance between good air flow to reduce mould, chemical smells etc and not too much to loose heat.
New house has no vents and no mould, but then is a cold place still. Blown in celulous fibre sucks, I prefer something that works and stays in place and doesnt compress over time. I know its environmentally friendly but it doesnt work as well.
GBD
Member
Something to be aware of when changing an older houses ventilation, ie - blocking off plaster vents, door seals etc, is the lower air movement can create the issues as noted above.
So while closing the vents reduces air losses, a totally airtight house needs to be designed properly to avoid mould / mildew and other off gassing issues.
So if the bathroom and kitchen area are still venting into the house or are not venting externally as much as they really should, then blocking the wall vents can potentially create a new issue.
So be aware that by blocking them - if the wall and ceiling insulation is insufficient or non existent - it might cause other issues.
Even totally airtight houses in Europe - have mandatory air exchange regulations -
So don't just lock it up like an esky !!
Or your home might just smell one. 
hamish05
Member
I started this post back in Feb and I thought that I should offer an update.
I blocked all the vents with Gap Seal with the intent of filling over when painting next, which will happen soon.
At the same time, I also sealed doors and windows. Evaporative cooler outlets were closed to all rooms, and new blinds were installed recently. See my post on window coverings, http://www.ata.org.au/forums/topic/2267
It is now near the end of winter and my next gas bill will indicate what savings I have achieved. However, in my mind I am sure I have stopped the many cold drafts that were previously apparent. I am sure that my central heating is not working as hard as it used to, and that will be reflected big time in my next account.
To date there isn't any sign of mould/mildrew on any walls, ceilings or around windows. I don't expect there ever will be, as the house open and bright by day and is dry as a result of our central heating, which in Melbourne's horrible winter is very useful.
peter69_56
Member
Congratulations a winner, not many seem to win. I am glad you have a good outcome. A win for the good guys. Enjoy
simplelife
Member
Hamish05 Please post your findings here!
I haven't blocked my vents yet, but I must mention that we have SERIOUS mould issues wherever we put any furniture/curtains/things against the walls-they turn black!
I ventilate the house everyday, but only some of the 1955 windows open...planning to rip them out and put in nice double glazed wooden replacements....
Should we consider a HRV unit essential to our plan?
jhamill
Member
i blocked mine up prior to getting an Hrv and had no mould/damp etc,even when i had a leak through the roof due to cracked tile, the ceiling dried off ok and no mould.
now I have an Hrv and i've also insulated under the floor boards (about 1 year ago) with polystyrene and polyester in the gaps below the skirting boards, so it's now reasonably draft free, but I would say not airtight, even with the hrv.
my house (california bungalow type) is about 4 feet off the ground at the back to about 1 foot at the front. I've got solar powered fans exhausting the sub floor area and it's bone dry in there now. when i first moved it was periodically damp, but still not apparent mould.
you probably need to work out why you are getting mould spores and fix the root cause before lowering your ventilation..is it damp beneath the house.
john
dmaunder
Member
I have a 100 year old WB house in suburban Melbourne, with a number of original decorative vents and was wondering how much heat they were letting in/out. I wouldn't want to cover them up completely, what is the best way to block up the holes without getting rid of the look of the vent from the inside?
hamish05
Member
For me it was simple. I just used “Gap Seal” filler and put a bead into the slots of the vent. You cannot see the filler from ground level.
I have noticed wall vents do vary in shape; mine are horizontal which made it a very quick and simple job to complete.
jhamill
Member
I used A4 plastic sheets (suggestion from somebody on this forum) that you get for binding A4 sheets into a folder and cut to size, then used double sided foam tape from bunnings. I did this over 12 months ago now and it is working well at stopping drafts etc. i've had 2 other vents plastered over entirely and it seems to have the same effect 'temperature' feeling wise as the plastic sheet.
simplelife
Member
Re-routed stormwater to ag pipe and drains around the house, washed the walls with Jif, blocked up plaster wall vents, moved furniture away from walls and all seems fine.
Still think there is a little moisture under the house, need to get under there again to see why, but we have had no more mouldy walls.
Now planning to replace windows with Double Glazed units.
They were required under the Gas plumbing regulations for rooms that had gas or oil heaters with naked flames.
People have died from carbon monoxide poisoning so the vents were there to stop this.
There is a school of thought that by not having vents and with the chemicals used in furniture manufacture ie custom wood glues, we are getting more allergies nowdays.
No one knew of gluton intolerence in the 40s.
Morbo
Member
blocked mine, but does not make a difference to the IR camera. Why? There is wiremesh behind full with dust. Plus the whole thing is just above the eave line, so the last 300 or so mm of your wall with the amazing insulation properties of 2 sheets of paper faces the most likely black roof tiles resp what ever night time temperature
amaizing corner detail
johnmath
Member
Morbo, the IR images only tell a part of the story. The images are showing the approximate temperature of the surfaces in the field of view (approximate because different materials have different emissivity properties). Heat transfer occurs by conduction and convection as well as radiation.
All surfaces radiate AND and simultaneously absorb heat according to their emittance properties and will heat or cool until such time as an equilibrium is met with the objects around it, ie the surface is absorbing radiant heat at the same rate as emitting it.
Conduction occurs when heat is transferred from a hotter surface to a colder one, in this case namely the layer of air adjoining the surface. If the air layer is constrained, such as in double glazing or behind heavy curtains, then the conduction slows dramatically once the surface air layer has reached (or fallen to) the temperature of the wall surface.
Convection is the transfer of heat by the movement of a fluid, in this case air. Hot (or cold) air displaces the air in the room and raises (or lowers) the room air temperature. A secondary but significant effect is that the air movement also increases conduction through the walls by disturbing the surface layer of air adjacent the walls, a mixing effect if you like.
The thermal images do not show air movement or air temperature, therefore do not illustrate the effect of blocking the vent, other than a minor secondary effect of the air flowing through the vent causing the vent itself to heat (or cool).
In the case of quantifying heat transfer due to room vents, thermal imaging has limited application.
hamish05
Member
Fab said:
They were required under the Gas plumbing regulations for rooms that had gas or oil heaters with naked flames.
People have died from carbon monoxide poisoning so the vents were there to stop this.
That maybe so, however the use of wall vents predates the introduction and general use of Gas and Oil heaters. (Showing my age here)
Wood fires may have been the culprit!
johnmath
Member
Morbo said:
There is 2 vents @0.1x0.2m, do you really think that will make more than academic difference?
No, I wasn't necessarily commenting on your circumstances. What makes the most difference is the addressing the dominant transfer mechanism, and that varies depending on circumstances - building materials, climate, wind, temperature differentials, etc, etc. What I was trying to say was that looking at thermal imaging will not necessarily show where or how vents may be a significant heat transfer mechanism, because thermal imaging does not "see" convection.
ncl_knight
Member
I have these in my house, built around the 1950's. I don't have an issue with them, apart from the dust that can come from them (and the odd spider).
Does anyone know if it is possible to get covers, which are screened, and allow you to shut them off in Winter, but open up in summer for better ventilation.
I have search all over the net, but had no luck tracking anything suitable down.
Regards one and all
alfresco24
Member
I found some adjustable louvre things at Bunnings that could fit over these vents but they're very very ugly. In my case I've gone and bought some stiff water clear plastic A4 paper 'wallets', cut them to fit snug inside the beveled edge and glued them in place with a tiny bead of clear silicon.
It retains the aesthetic look and keeps out drafts and dust.
The amount of dust build-up behind them is quite large already (if you get up close and look closely) and by the bulging/sucking movement it's obvious that air pressure changes drives a fair bit of air through these suckers.
I didnt cover the wall vents that open to corridors in my case as this will assist with the evap cooler air flow just a little bit.
