Condensation on inside of new windows

kwat

Apologies if this has been covered before.

Had work done on my Dublin12 mid-terrace last year which included external insulation and new windows (triple glazed at the north facing back). House is much warmer, the BER is up to B2, which is great.

I (stupidly) didn't opt for trickle vents in the windows as there are wall vents in each room so thought this would be sufficient, however on colder winter nights I'm getting some condensation on the windows (just around the bottom edges of the glass).

Is there anything I can do to remedy this? The wall vents are open at all times and as I said it's only on cold nights this happens.

MicktheMan

A simple centralised mechanical extraction ventilation system linking as many wet rooms as practical should remedy this.

Or

Open some windows a crack when needed.

kwat

https://www.boards.ie/discussion/comment/121766617#Comment_121766617

Thanks. The second option sounds simplier than the first somehow!

Anaki r2d2

https://www.boards.ie/discussion/comment/121766617#Comment_121766617

Hi, what would you recommend as a simple mechanical ventilation system? Any products and places to buy would be appreciated

Thinking of doing this as a diy project

User567363

Dehumidifier?

I have 2 one for the bathroom after showers and one for the hall for drying clothes

They are automatic and turn on when humidity is above 55

No condensation and no heat lost by over ventilation, infact the devices slightly warm the rooms as they dehimidify

Redlim

https://www.boards.ie/discussion/comment/121766617#Comment_121766617

Sorry to hijack. Would a centralised mechanical extraction system be feasible in a dormer bungalow? I know it would be very tricky to link to downstairs rooms but would a link to the landing help the downstairs?

If it's feasible, would you have even a rough idea of what these systems generally cost to install?

Our bedrooms and bathrooms layout is as follows:

3 * beds upstairs, 1 downstairs

1 ensuite + 1 bathroom upstairs, 1 bathroom downstairs

kwat

https://www.boards.ie/discussion/comment/121768874#Comment_121768874

It's an option, but the condensation is in 4 rooms so would need one in each room.

As I said, it's only around the bottom edge of the windows and only there the next morning when the temperature drops outside, so not that often this winter as it's been pretty mild.

I usually just wipe the moisture away. An option is to leave the window slightly ajar I guess, or maybe leave those small moisture collectors in the window?

It's just a little frustrating after spending so much on the windows and external insulation to have this problem (should have got the trickle vents).

con747

https://www.boards.ie/discussion/comment/121768933#Comment_121768933

Trickle vents would have done very little, I have them and in the same situation as you so following the thread.

MicktheMan

https://www.boards.ie/discussion/comment/121768837#Comment_121768837

I recently (last year) bought one of these online from the Netherlands, €260 delivered, perfect for diy. Got insulated ducting locally. System is fully configurable depending on house size.

tomhammer..

https://www.boards.ie/discussion/comment/121769014#Comment_121769014

What's the advantage over a dehumidifier or how does it work

MicktheMan

https://www.boards.ie/discussion/comment/121768924#Comment_121768924

Depends very much on layout / access but generally yes.

It is advisable to have an extract in each room with a tap/sink but even if only the upstairs wetrooms can be ventilated, this will still make a huge difference to the house. As with any central ventilation system, ensure there is a decent gap under all internal doors when closed (min 15mm is generally recommended).

On costs, see previous post on equipment and generally a days labour to install so shouldn't be expensive.

On a separate note, how air tight is your dormer? (Dormer's are notorious for heat loss due to higher than normal air leakage!)

MicktheMan

https://www.boards.ie/discussion/comment/121769100#Comment_121769100

Did I say there was an advantage?

I have no experience of using a dehumidifier regularly to get rid of moisture. I know some people do.

However, I do know they can be noisy and relatively heavy on electricity.

Ventilation works most efficiently by replacing relatively 'wet' internal air with relatively 'dry' external air at a low level on a continual basis during the heating season. Passive ventilation ('hole in wall' / window trickle vents) has been proven to be less than effective in our climate.

Anaki r2d2

https://www.boards.ie/discussion/comment/121769014#Comment_121769014

Thanks. What type of ducting did you get? Any links for that?

Drop the extraction points into the wet rooms. Exhaust down throught the soffit?

When you say configurable, is there much to balancing the flow through each room?

I am in the same position as the OP. Retrofitted 1995 built house. Now warm but condensation on the cold days

Redlim

https://www.boards.ie/discussion/comment/121769116#Comment_121769116

Great info, thanks.

In relation to our air tightness/heat loss you're probably going to really dislike what I say next - we have spray foam (with vent cards) in the attic and crawl spaces. Gable walls in the attic are spayed also. Sloped ceilings in upstairs rooms not upgraded though. It really has made a massive difference to the heat loss as it's not leaky anymore.

We know we need to better ventilate the house now though since there's less natural air exchange. I'm just confused as to what's needed though. Given that the attic is practically sealed off I'm thinking we'd need the air intake for any system to go through the gable wall in the attic.

MicktheMan

https://www.boards.ie/discussion/comment/121769176#Comment_121769176

Insulated flexible ducting from Lindab. Think about when the unit will be installed to try to minimise the duct run lengths.

Exhaust should ideally be through a roof vent tile/slate or a gable wall if available.

Configurable in the sense that different extract rates can be configured depending on house size/volume. Balancing individual rooms, if needed, can be done at the ceiling valves by adjusting the valve to suit.

Anaki r2d2

Thanks Micktheman. How do you know how to balance the rooms? Is it by feel/sound or with some measurement method?

Why not through the soffit for the exhaust?

MicktheMan

https://www.boards.ie/discussion/comment/121769306#Comment_121769306

I use intuition plus trial and error. I first note which room have the longest duct runs then the moisture generating intensity of each room and open the valve most for the intensive / longer duct rooms and less for the shorter / less intensive rooms and then see if I'm happy with the result. If not, then adjust where needed until happy.

(There are specialised air flow assemblies to measure air flow accurately which are used by the ventilation companies.)

The exhaust duct going outside should, imo, be always rising to a) prevent the buildup of any moisture within the duct and b) work with nature (warm air will naturally want to rise). Running it horizontally over joists runs the risk of water buildup / trapping within the duct and in extreme situations can cause a blockage to occur between joists.

tomhammer..

So this is low level mechanical extraction?

What happens then during a bath or shower when theres masses of steam produced?

MicktheMan

https://www.boards.ie/discussion/comment/121769646#Comment_121769646

It automatically increases in speed to extract at a faster rate.

smyth79

https://www.boards.ie/discussion/comment/121772645#Comment_121772645

Is there just one fan in the unit? So if it detects the humidity coming from the shower the extraction speed increases for all rooms that have an extraction vent?

I am considering a similar system for my house renovation and extension. Just trying to figure out if there would be more heat lost through a centralised system like this than would be lost through individual extractor fans.

MicktheMan

https://www.boards.ie/discussion/comment/121802766#Comment_121802766

Yes, single fan system.

The level of heat loss from the extracted air is minuscule in the round (don't overthink it).

tomhammer..

Surely separate fans/humidistats is prefererable to boosting extract simultaneously for all wetrooms

listermint

https://www.boards.ie/discussion/comment/121769213#Comment_121769213

All ventilation systems requires access to external extract or and external supply.

In your case you'd need to go through somewhere to the outside world be it gable or roof.

Gable is preferred as roof brings a host of complexities and future leak potential gable is simpler all things considered.

smyth79

https://www.boards.ie/discussion/comment/121803385#Comment_121803385

Ok thanks.

Can feel cold air being pulled in through the vents in the winter time? I am happy that this system would meet the house's ventilation needs. I just don't want to feel cold draughts after upgrading the airtightness as best I can.

Redlim

https://www.boards.ie/discussion/comment/121803439#Comment_121803439

Thanks, I was thinking the gable would be better alright.

If I remember correctly you have a PIV system? I'd like to do something in the next few months to improve the fresh air levels but I'm a little confused as to what's best, or even what's best bang for buck. I've seen some people mention the PIV may have an unwanted side effect of pushing moisture into the leaky bits of the building fabric - no idea how significant a problem that is though. How have you found it so far?

@MicktheMan does the system you linked to above work in both directions, i.e. it extracts but can it also reverse and introduce fresh air? Did you install it for yourself or as part of a job, and did you consider a heated version?

tom1ie

https://www.boards.ie/discussion/comment/121768874#Comment_121768874

What dehumidifiers are you using? I’m looking to get one myself and I like the idea of an automatic humidity setting.

listermint

https://www.boards.ie/discussion/comment/121803668#Comment_121803668

No I have a MHRV system Adroit DV145 big investment.l, It's not a PIV which tend to be more entry level solutions but reasonable value.

MicktheMan

https://www.boards.ie/discussion/comment/121803518#Comment_121803518

I'm confused by your question... I'm talking about an extraction system ... in any case, the level of air flow will not be noticeable

MicktheMan

https://www.boards.ie/discussion/comment/121803668#Comment_121803668

does the system you linked to above work in both directions, i.e. it extracts but can it also reverse and introduce fresh air? No, it is an extraction system.

Did you install it for yourself or as part of a job, Self install in my daughter's dwelling

and did you consider a heated version? No, the heating system deals with heating efficiently and besides using air to add space heating as part of a ventilation system won't work because the level of air flow wouldn't amount to much heating unless you are talking about achieving passive house standard certification for the building.

Anaki r2d2

There is a bit of confusion on this thread.

PiV = positive internal ventilation. A fan that blows fresh air from outside into the house. This positively pressure pushes air out through vents or gaps in the house. This can be heated a little. The incoming air is cold [if its cold outside]

Single extractor fans suck air through the fan and exhaust outside the house.

Mechanical ventilation is a large single fan pulling from mutiple rooms. Typically running on low flow 24/7. No heating element on this system

MHRV = mechanial heat recovery with ventilation. Large fan pulling g stale air from wet rooms. Pushing fresh air to habital rooms. Stale air used to warm fresh air via a heat exchanger. Normally installed in airtight house.

If the house has 4 inch wall vents it's not air tight

Gusser09

Im seeing this issue a lot more. Wall vents not really helping with condensation. And all they really do is let cold air in a raise heating bills.

Leave your internal doors open for circulation for a start.

Ensure the rooms you are having the problem in are constantly heated.

I have a B2 rated house and have a pain in my hole heating it.