Ventilation in new builds.

Tar.Aldarion

I am wondering how this works, as I just moved in and while looking I don't seem to have vents anywhere. How do these things work these days, I know that the place is supposed to be airtight and so on, are they concealed in the floor/wall/ceilings? Should I be opening windows ever or is there no need?

Penn

There are a few different ways the property may be designed. Is there a Mechanical Ventilation Heat Recovery System or Positive Input Ventilation system installed in the property? If so there are likely ceiling vents in the rooms which supply fresh air and heat. Wall vents or window trickle vents would prevent the MVHR system from operating correctly. However if there is no mechanical ventilation system, then yes there should be some form of background ventilation by way of wall vents or trickle vents built into the windowframes. I believe wall or trickle vents are still required for a PIV system.

Are there any ceiling vents in habitable rooms?

Tar.Aldarion

I'm not sure what those are so I'll have to google to see, my heating is via an air to water system, underfloor and rads. I can see circular extraction vents in bathrooms, but no vents anywhere else. Perhaps there are some I can't see or haven't noticed in the windows or otherwise hard to spot

Biker1

There is a requirement in the building regulations that all buildings are adequately ventilated. How this is achieved is outlined in Part F and PIV is not one of the options. If there are no visible ventilation valves in the ceilings or no wall vents and extractors in the wet rooms then you do not have adequate ventilation.

kippy

https://www.boards.ie/discussion/comment/120069826#Comment_120069826

One would hope that a professional snaggger or surveyor would have picked this up in their report assuming one was done.

Penn

https://www.boards.ie/discussion/comment/120069811#Comment_120069811

The vents in the bathroom (and I'm presuming kitchen) extract air from those rooms as they're rooms with higher levels of moisture. In an MVHR system, there would also be vents in bedrooms where the warm air from bathrooms/kitchen are used to heat incoming air to the bedrooms/living rooms etc. That's the Heat Recovery part of the system.

If there are no similar ceiling vents in bedrooms/living rooms, then I would suggest checking the window frames thoroughly. If there are definitely no vents built into the frames, then there would appear to be inadequate ventilation. As it's a new build, you should check with any professional you may have engaged for a pre-purchase building survey or similar, or if not you should discuss with the vendor and ask how Part F (Technical Guidance Document regarding Ventilation) is complied with.

Tar.Aldarion

Thanks so much guys, I found that there are small vents at the top of the windows that you can shut or open, they were shut and just look like a part of the window so you would never know they were there without looking for them. I presume these should be open fully or at least partially all the time.

Penn

https://www.boards.ie/discussion/comment/120069904#Comment_120069904

Yes, those are trickle vents for background ventilation and should be kept open unless there's a significant reason to have it closed for a short period of time, after which it should be opened again (as having them closed for a long period of time results in a buildup of moisture in the air and can lead to condensation and mould growth). Provided the vents are sized accordingly (which I would assume they are), that likely satisfies the requirements for ventilation.

Also try to ensure they're not blocked/restricted with blinds fitted too closely to the frame as it can prevent air circulation through the vent.

10-10-20

Leave them open for the most part but close them off if there is a cold gale blowing or the room feels excessively chilly. You should invest in an temperature / RH meter for a few rooms and use that to manage the relative humidity around the 50% to 55% mark.

Today is a humid day - my bedrooms are all at 62% as it's relatively warm and damp outside - so nature will control the RH for a good part.

Tar.Aldarion

Thanks guys. I bought a basic temp/humidity monitor last week actually as my stats dont report the correct temp at all, and just had a pipe burst 2 nights ago so been using that to measure the humidity. Will move it around the rooms, they were about 60% downstairs (74% after pipe incident) but have never checked upstairs.

Biker1

If this is a new build under the current building regulations then you can only have natural ventilation if the airtightness test result is between 3 & 5m3/hr/m2. Supposing it is between these two figures then the vents in the windows would definitely not be big enough to provide the correct background ventilation.

Penn

https://www.boards.ie/discussion/comment/120070241#Comment_120070241

I'm not sure what you're basing that on with no indication regarding the number of trickle vents, size of trickle vents, number of rooms, floor area of dwelling.

TGD F

1.2.4.1 Where the air permeability is greater than 3m3 /(h.m2 ) and lower than 5m3 /(h.m2 ), the minimum total equivalent area of background ventilators providing general ventilation should be 42,000mm2 with an additional 7,000mm2 for each additional 10 m2 floor area above the first 70m2 of floor area measured. 

A 100mm.dia wall vent gives just under 8,000mm2. A 500x13mm trickle vent (conservative given trickle vents may be longer or wider) gives 6,500mm2. So it would come down to the size and number of vents provided, as well as floor area.

Biker1

https://www.boards.ie/discussion/comment/120072442#Comment_120072442

While the 100mm diameter pipe may have an opening of around 8,000mm2 the actual area accounted for is what comes through the grille over it. This has to be a certified area and if not then is calculated as being 25% smaller. Same goes for window vents. So unless the rooms are tiny then it is highly unlikely that the ventilation rate is correct by either method.

Tar.Aldarion

How long would it take issues to show up? The house has been sat empty for over a year when built, moved in 1.5 months ago and all good, no condensation or anything.

10-10-20

https://www.boards.ie/discussion/comment/120074303#Comment_120074303

What specific issues are you thinking of?

Tar.Aldarion

I mean if he saying a building may not be appropriately ventilated by these vents, how will that manifest? Things seem fine.

MicktheMan

"how will that manifest?"

Several ways (some more obvious than others):

• surface condensation, damp & mould
• mould growth on clothing / furnishings especially natural products such as leather
• wall & roof insulation damper than it should be resulting in significant drop in performance
• I understand high relative humidity is also linked to dust mite population and dust mite faeces is linked with asthma health issues

awec

https://www.boards.ie/discussion/comment/120075351#Comment_120075351

Your house sounds similar to mine, the only vents are the trickle vents at the top of the windows. No issues here.

Generally we leave them open early Spring until about November time when draughts start becoming noticable, during the winter they are closed more than they are open, no issues with damp or mould (we've been here for nearly 4 years now). The bathroom trickle vents stay open all year round.

Tar.Aldarion

Cheers! Sounds grand, my bathrooms don't have windows, just skylight things that aren't open-able, so may leave their adjoining bedroom vents more open to compensate.

Penn

https://www.boards.ie/discussion/comment/120086191#Comment_120086191

I'd advise against that, as the air in the bathroom will have more moisture and you risk causing condensation/mould in your bedroom. While your bathroom doesn't have any background vents, going by your previous posts it does have a mechanical extract vent in the ceiling. This vent likely has a sensor built in for humidity, so it kicks in when it's needed. That will provide the required ventilation for the bathroom.

Tar.Aldarion

Thanks, yes they do, all of them are fine apart from one where I am beginning to see a crack in the paint, a line

Penn

I wouldn't be overly concerned about the cracking shown. Some level of cracking is normal in the first 6-12 months of a new build and is commonly down to dry-shrinkage; where the moisture in the building finishes continues to dry out over time and causes shrinkage. You're probably okay to sand down and fill in the cracking and repaint, and if it re-appears then further investigation may be required.

But yes, that extract vent should be sufficient to ventilate the bathroom, so I'd recommend closing the bathroom door when not in use and the sensors in the extract should ventilate the room without the need for any background ventilation.

awec

Those vents are probably just running constantly rather than having a sensor (at least that's what mine do).

Experts on here will know better than me but that crack looks a bit suss to me, it looks bigger than what you'd normally see from minor board movement over time, like there's weight being put on the board from above (from the vent). Could just be the photo though.

Tar.Aldarion

Thanks, it appears to be growing with shower use, so I'll keep an eye on it. The vent itself does appear to have a humidity detector as it turns on after showers (though they are so quiet you have to listen out for it).

muffler

https://www.boards.ie/discussion/comment/120086481#Comment_120086481

That might be just a "run on" after each shower. If there's a sensor the fan will kick in when using hot water in the basin for a periodor generally when moist air is present..

Tar.Aldarion

Oh, will have to do some tests to see! Barely would use the basin enough yet to know that.