I am planning to replace the original fascias and soffits on my house, which was built in 1994. Several companies have provided estimates and have specified ventilation equivalent to a 10mm continuous gap, in accordance with the current building regulations. However, I believe the original soffits have more ventilation than this. The soffits have rectangular ventilation slots at regular intervals. Each 61 cm along the length of the soffit has a 22 cm long ventilation slot, and each slot is 48mm wide. This is equivalent to (22/61)x48 = 17 mm continuous gap. Although there will be a correction factor to take account of the fact that the slots have a wire mesh grille, I suspect the ventilation is still more than the equivalent of a 10mm continuous gap.

A few years ago, I had trouble with condensation forming in the loft in cold weather. I reduced the problem significantly by fitting a tighter-fitting loft-hatch and sealing around pipes/cables where they enter the loft from the rooms below. Now only a few drops of condensation form on the roofing felt in cold weather. However, I do not want to aggravate condensation issues by having new soffits/fascias that provide less ventilation than the existing ones. Therefore I'm thinking of either (i) using soffits that provide ventilation equivalent to a 25mm continuous gap, or (ii) using soffits that provide ventilation equivalent to a 10mm continuous gap plus over-fascia ventilation that provides ventilation equivalent to an additional 10mm continuous gap.

I'd be grateful for any comments about whether (i) or (ii) above sound sensible, or if there are any reasons why I should not use these options

thanks

John

JohnD wrote:
I am planning to replace the original fascias and soffits on my
house, which was built in 1994. Several companies have provided
estimates and have specified ventilation equivalent to a 10mm
continuous gap, in accordance with the current building regulations.
However, I believe the original soffits have more ventilation than
this. The soffits have rectangular ventilation slots at regular
intervals. Each 61 cm along the length of the soffit has a 22 cm long
ventilation slot, and each slot is 48mm wide. This is equivalent to
(22/61)x48 = 17 mm continuous gap. Although there will be a
correction factor to take account of the fact that the slots have a
wire mesh grille, I suspect the ventilation is still more than the
equivalent of a 10mm continuous gap.

A few years ago, I had trouble with condensation forming in the loft
in cold weather. I reduced the problem significantly by fitting a
tighter-fitting loft-hatch and sealing around pipes/cables where they
enter the loft from the rooms below. Now only a few drops of
condensation form on the roofing felt in cold weather. However, I do
not want to aggravate condensation issues by having new
soffits/fascias that provide less ventilation than the existing ones.
Therefore I'm thinking of either (i) using soffits that provide
ventilation equivalent to a 25mm continuous gap, or (ii) using
soffits that provide ventilation equivalent to a 10mm continuous gap
plus over-fascia ventilation that provides ventilation equivalent to
an additional 10mm continuous gap.

I'd be grateful for any comments about whether (i) or (ii) above
sound sensible, or if there are any reasons why I should not use
these options

They have supplied prices with a 10mm vent strip because this is what most
homes have and is normally adequate.
If you'd asked for a 25mm strip they'd have priced for it, although there's
only pennies different:
http://www.roofingsuperstore.co.uk/b...fit-vents.html

On Saturday, May 24, 2014 6:20:31 PM UTC+1, Phil L wrote:
JohnD wrote:

I am planning to replace the original fascias and soffits on my

house, which was built in 1994. Several companies have provided

estimates and have specified ventilation equivalent to a 10mm

continuous gap, in accordance with the current building regulations.

However, I believe the original soffits have more ventilation than

this. The soffits have rectangular ventilation slots at regular

intervals. Each 61 cm along the length of the soffit has a 22 cm long

ventilation slot, and each slot is 48mm wide. This is equivalent to

(22/61)x48 = 17 mm continuous gap. Although there will be a

correction factor to take account of the fact that the slots have a

wire mesh grille, I suspect the ventilation is still more than the

equivalent of a 10mm continuous gap.



A few years ago, I had trouble with condensation forming in the loft

in cold weather. I reduced the problem significantly by fitting a

tighter-fitting loft-hatch and sealing around pipes/cables where they

enter the loft from the rooms below. Now only a few drops of

condensation form on the roofing felt in cold weather. However, I do

not want to aggravate condensation issues by having new

soffits/fascias that provide less ventilation than the existing ones.

Therefore I'm thinking of either (i) using soffits that provide

ventilation equivalent to a 25mm continuous gap, or (ii) using

soffits that provide ventilation equivalent to a 10mm continuous gap

plus over-fascia ventilation that provides ventilation equivalent to

an additional 10mm continuous gap.



I'd be grateful for any comments about whether (i) or (ii) above

sound sensible, or if there are any reasons why I should not use

these options



They have supplied prices with a 10mm vent strip because this is what most

homes have and is normally adequate.

If you'd asked for a 25mm strip they'd have priced for it, although there's

only pennies different:

http://www.roofingsuperstore.co.uk/b...fit-vents.html

Thanks Phil, that sounds like the best bet

JohnD wrote:

However, I do not want to aggravate condensation issues by having new
soffits/fascias that provide less ventilation than the existing ones.

Maybe that wouldn't actually cause a problem, after all the water that was
condensing has to have come from somewhere. Less ventilation might also
mean less wet air coming in.

--
Jeremy C B Nicoll - my opinions are my own.

Email sent to my from-address will be deleted. Instead, please reply
to replacing "aaa" by "284".

replying to JohnD , jaxonmackinolty wrote:
We have replaced our 10 year old ventilation system with Ventis
ventilation system. I have read customer reviews about Ventis on many
sites and impressed after watching its complete working on you tube.

--