Ventilation

jethrothe2nd

We've done a good bit of work on the house to make it as energy efficient as we can, including attic insulation, new windows and doors, closing up gaps that were letting in drafts etc. We now need to do something about ventilation, particularly upstairs. The previous owners had the vents in all three bedrooms sealed up, so the only ventilation is the trickle vents on the windows which aren't enough don't stop a small amount of condensation on the inside of the windows. The ensuite bathroom has a vent, and an extractor fan, neither of which stop mould growing on the ceiling, and I would like better extraction in the main bathroom as there is no window in there being a terraced house.

Would a demand control ventilation system be appropriate, or would there be any better solution?

DOCARCH

First thing to do is open up the closed vents!

The old adage is the more you insulate, the more you ventilate.

Then, if you want to have a look at something more, have a google/look at positive input ventilation. For an existing house, easier/more straightforward to install than demand control ventilation.

riddles

https://www.boards.ie/discussion/comment/121251168#Comment_121251168

I am in the same boat - the house only has trickle vent in the windows and zero wall vents.

How many wall vents would be recommended in a four bed detached?

Would the positive input ventilation system work on the upstairs only? thanks

MicktheMan

Imo, cMEV is a superior solution to PIV for the simple reason that the moisture is being extracted through dedicated ductwork rather than being partially forced out through a progressively cooler building structure risking condensation at and beyond the dew point (essentially pumping moisture into the structure). PIV would generally be cheaper to install though (but cheaper is not always better in my book).

DCV would be a step up from cMEV and generally needs a decent level of air tightness to get the benefit of the extra investment.

Asdfgh2020

https://www.boards.ie/discussion/comment/121251348#Comment_121251348

Can you expand the acronyms please….not all of us are au fait with the industry speak…😀

MicktheMan

cMEV - centralised Mechanical Extraction Ventilation

PIV - Positive Input Ventilation

DCV - Demand Control Ventilation

https://www.boards.ie/discussion/comment/121251648#Comment_121251648

With the cMEV, would you recommend this just for bathrooms, or also extraction in bedrooms etc?

We have 4 inch vents on all rooms. Inline fans in bathrooms. But this week, the double glazed windows have a lot of condensation. So much so that we have a karcher window vac to get rid of it.

MicktheMan

https://www.boards.ie/discussion/comment/121251727#Comment_121251727

Generally you extract from wet rooms (bathroom, en-suite, utility, kitchen).

Regarding the condensation on your windows, bare the following in mind before choosing to do something; Ventilation depends on the temperature differential between inside and out. In the warmer summer months when there is little difference in temps, the moisture generated indoors is absorbed into the fabric of the house. One of the side effects of this is swelling of natural materials such as timber which can cause doors to stick. Then when Autumn arrives with sudden cooler weather (larger temperature differential), the house starts to dry out and the moisture tries to get out but encounters very cool glazing surfaces and thus condenses (the sticky door also magically becomes free). This is quite normal and most houses have this happening this time of year and gradually the condensation will more or less disappear over a few weeks depending on the weather. Where you have an issue which needs attention is when this condensation on the glazing persists for months well into the winter.

https://www.boards.ie/discussion/comment/121251951#Comment_121251951

Thank you for taking the time to reply.

For others above posting. House is 25 years old. Cavity walls. PVC double glazing. Walls recently pumped with beads. Attic has 8 inch of insulation. New composite external doors. Was a D2 now a C1. Heating controls etc helped with rating

jethrothe2nd

This has

https://www.boards.ie/discussion/comment/121251951#Comment_121251951

This makes a lot of sense. Thank you. I'm looking at it in a different light now, and perhaps DCV would be a sledgehammer to crack a nut. I think I will begin by getting better extraction in the bathrooms, and for the moment, just watch more closely what is happening on the windows in the bedrooms over the next few weeks.

Alkers

Unblock the bedroom vents as a first step.

Have a look at your bathroom fan in the first instance. We installed a humidity controlled fan which runs slowly all the time, drawing out air from the bathroom and in turn, fresh air in through the bedroom vents. If you don't have a window in your bathroom you will need to make sure there is a 1-2cm gap under your bathroom door to allow air in so your extractor can remove damp air while shower is in use.

You can then consider replacing the "dumb" vents in bedrooms with dcv ones eg from aereco, which mechanically vary the opening size based on the local humidity

Quango Unchained

For retrofit ventilation of a 3 bed 2 storey semi, without having ducting, could someone please help with listing the various options?

1. Passive (hole in the wall) vents in bedrooms and sitting room + mechanical extractor fans in bathroom (run off light-switch?) and kitchen (extractor hood)
2. Demand controlled non-mechanical (non-wired) independent vents in bedrooms and sitting room that use humidity detecting strips such as Aereco that widen / narrow based on the humidity + mechanical extractor fans in bathroom (run off light-switch) and kitchen (extractor hood)
3. Heat recovery hard-wired vents with ceramic core, that cycle between extracting air for X seconds (which warms the ceramic core) and taking in air for X seconds (which is warmed in turn by the ceramic core) and have WiFi for synching with partner vents for air-flow, for bedrooms and sitting room and possibly bathroom - search for "NZEB Retrofit on line Single Room Heat Recovery Ventilator" on youtube for a short video. Not sure if this type of vent would work for the bathroom. The kitchen would just have a standard extractor hood or possibly both a heat recovery vent as well?