Ventilation.. do I need ducting?

[fiskrond]

Imagine if you will.. small stone built terraced house, shallow pitched roof.
Upstairs get's far too warm in summer... I have a portable aircon unit in bedroom so I can sleep (proper one)... but I digress..
The roof has 2 ventilation tiles on each side.. 4 total.
Attic hatch is in bedroom where I am running aircon unit.... hatch is a mere 330mm x 430mm.

So.. the ventilation question is...

If I installed an extractor unit (as bathroom/kitchen) into the attic hatch, would it need any ducting or would the vent tiles handle the increased air-flow?

 

[SFK]

Fiskronf,
You should/must not allow air from house to go into loft. The air in the house is warm and moist, and when/if it gets into the colder loft the moisture in the warm air will condense in the cold loft causing damp and mould.

So yes, you defently need a duct to go from fan, through the loft, to outside.

Sfk

 

[^woody^]

You need to duct the air to external.

 

[Ian H]

Is the roof space getting hot and warming the bedroom?

If it is i’d ventilate more up there and increase the insulation on the loft floor.

 

[catlad]

What is on the roof.

 

[fiskrond]

@catlad
concrete(?) tiles.. not slates. Internal membrane.

@Ian H
Overheating problem started when I had the loft insulated a few years ago... there's about 9" of shredded Honey Monster up there!

@SFK
I suspect the void is probably warmer than the house during the 6-8wks of stupid weather that we get in UK in summer... would condensation still be an issue if fan only in use during that period? Would seal it off during cooler months so as to prevent warm humid air rising into the attic.

All advice appreciated.. am at wits end. Currently exploring UV film options on windows on the SW side of house to limit heat penetration in first place.
House was cold in winter due to no attic insulation... however it is now costing me more in air-con (can't sleep in +28c) in summer than the supposed saving on winter heating... bah!

 

[noseall]

The loft ceiling insulation will only serve to protect from external heating from the sun. You obviously need more on the loft ceiling or better gear at least. Your (south facing) walls are prolly suffering too.

 

[Ian H]

The loft ceiling insulation will only serve to protect from external heating from the sun. You obviously need more on the loft ceiling or better gear at least. Your (south facing) walls are prolly suffering too.

 

[Ian H]

Sorry, wrong thread!!

 

[noseall]

All done

15544557804641042502957

• noseall
• 5 Apr 2019

 

[SFK]

Fiskronf,
To your question "suspect the void is probably warmer than the house during the 6-8wks of stupid weather that we get in UK in summer... would condensation still be an issue if fan only in use during that period? Would seal it off during cooler months so as to prevent warm humid air rising into the attic." - I don't know, but would be worried that you would forget and on cold mornings in the summer you will get condenstation.

But have experiensed similar issues with single skinned or solid outer walls where the entire external walls in room have been like boiling hot or freezing cold radiatiors as the outside cold/sun hits the wall and the cold/heat has passed straight through the wall into the room. I had to put layer of kingspan and plasterboard on wall to minimise effect.

SFK

 

[arkie]

When mine was insulated from 10cm to 30cm (i think) and cavity walls was done the same day, within 3 days i had pulled back the loft rolls over both large bed rooms a strip of 2m x 4m down the bedrooms dividing wall, It was a hot box upstairs that open windows could not help with, insulation is meant to keep a house cool in summer but that is not what i found.


I really don't think a bath fan will do the job, far to small, But if you want to try it just make a new hatch lid out of plywood/chipboard, cardboard if it comes to it. If you don't have any vent pipe i think you will end up with dust and the attic insulation coming down on you.


More vent tiles can only help, Are the eves clear? And have you ever measured the temp up their?

 

[Leofric]

I really don't think a bath fan will do the job, far to small, But if you want to try it just make a new hatch lid out of plywood/chipboard, cardboard if it comes to it. If you don't have any vent pipe i think you will end up with dust and the attic insulation coming down on you.

extract fan in loft hatch , cardboard hatch lid
Best to try following (or get somebody who knows about such things to inspect the property and advise you ) Bldg Regs Approved Documents on background, purge/rapid, mechanical extract ventilation, thermal insulation, ventilation of roof space , draughtstripping/sealing loft hatch, and recommendations in other recognised publications on thermal insulation/condensation avoiding the risks etc.
ps The hatch isn't big enough to comply with current requirements of course.
pps the south facing rear of my house with patio doors is much warmer than the north facing front of the house ,the living room at the front is distinctly cooler ,but that is to be expected .

 

[fiskrond]

Fiskronf,
To your question "suspect the void is probably warmer than the house during the 6-8wks of stupid weather that we get in UK in summer... would condensation still be an issue if fan only in use during that period? Would seal it off during cooler months so as to prevent warm humid air rising into the attic." - I don't know, but would be worried that you would forget and on cold mornings in the summer you will get condensation.

But have experiensed similar issues with single skinned or solid outer walls where the entire external walls in room have been like boiling hot or freezing cold radiatiors as the outside cold/sun hits the wall and the cold/heat has passed straight through the wall into the room. I had to put layer of kingspan and plasterboard on wall to minimise effect.

SFK

Ahhh.. that makes a lot of sense and do-able... had been considering solar-reflective paint on the outside but unable to find much info other than sales blurb from companies selling the stuff (obviously biased and subject to many pinches of salt!)

 

[fiskrond]

When mine was insulated from 10cm to 30cm (i think) and cavity walls was done the same day, within 3 days i had pulled back the loft rolls over both large bed rooms a strip of 2m x 4m down the bedrooms dividing wall, It was a hot box upstairs that open windows could not help with, insulation is meant to keep a house cool in summer but that is not what i found.


I really don't think a bath fan will do the job, far to small, But if you want to try it just make a new hatch lid out of plywood/chipboard, cardboard if it comes to it. If you don't have any vent pipe i think you will end up with dust and the attic insulation coming down on you.


More vent tiles can only help, Are the eves clear? And have you ever measured the temp up their?

Temp up there right now is 8c, bedroom is 12c. Heating hasn't been on for a few days... is a bit nippy!
I went from no insulation whatsoever... have considered using a rake to pull out as much as I can reach. Or sending a 6yr old up there.. lol