Worth replacing Velux roof windows

Ricey3509 · 31-12-2020 7:55pm #1

Hi,

We've got 3 Velux roof windows (18 years old) in a lean to extension on our house. I've noticed in the last year or so that the room (open plan living/kitchen) seems to lose heat quite quickly once the heating is off , the roof itself was reinsulated about 7 years ago and windows / sliding doors were replaced with DG AluClad at the same time. So perhaps the Velux are past their sell by dates and its time to replace them? I had a look at the Velux web site and it looks like around 630 each (plus fitting) to replace them with a triple glazed unit.

Should I consider getting someone in to do a test (thermal/air tightness)?

Thanks!

greasepalm · 31-12-2020 8:05pm

Might be worth it if replacing wrong item.

Outkast_IRE · 31-12-2020 8:09pm

There is a significant difference in the newest velux Vs 20 years old . Worth replacing in my opinion . Have a a look at the finishes also the newer velux come in a few different finishes the white finish is maintenance free essentially which is a big boost no painting or weathering of the wood

Ricey3509 · 01-01-2021 3:12pm

Thanks for the responses, I'll get in touch with a roofer we've used before and get a concrete price on replacement.

On the subject of an air tightness test if anyone has any recommendations for someone to do this in North Dublin feel free to drop me a PM.

Outkast_IRE · 01-01-2021 6:18pm

Ricey3509 wrote: »

Thanks for the responses, I'll get in touch with a roofer we've used before and get a concrete price on replacement.

On the subject of an air tightness test if anyone has any recommendations for someone to do this in North Dublin feel free to drop me a PM.

What are you hoping to get out of the airtightness test ?

In most properties it will come back with generic stuff like - Windows Seals & Hinges , Door Seals, Unused chimneys etc. Any obvious gaps to the attic such as poorly fitted attic hatch etc.

Alot of stuff you may wish to tackle yourself because outside of that stuff if anything else is picked up it may not be fixable easily. For example in my own home standard 3 bed semi in an estate, the plasterboards are put on the external walls with the dot dab technique giving a gap between the board and the wall often showing up a draft by the skirting or windowboards - generally not easily fixable really, but some tidy caulking around the skirtings etc can minimise it.

Calahonda52 · 01-01-2021 6:45pm

Outkast_IRE wrote: »

What are you hoping to get out of the airtightness test ?

In most properties it will come back with generic stuff like - Windows Seals & Hinges , Door Seals, Unused chimneys etc. Any obvious gaps to the attic such as poorly fitted attic hatch etc.

Alot of stuff you may wish to tackle yourself because outside of that stuff if anything else is picked up it may not be fixable easily. For example in my own home standard 3 bed semi in an estate, the plasterboards are put on the external walls with the dot dab technique giving a gap between the board and the wall often showing up a draft by the skirting or windowboards - generally not easily fixable really, but some tidy caulking around the skirtings etc can minimise it.

have you checked to see if the wall vents are ducted out to the outer face of the PB and are air sealed

Ricey3509 · 05-01-2021 10:20pm

Got a quote of €3100 to replace the 3 , not sure if that’s good ( seems a little high to me?) so l’m hoping to get another quote this week.

No obvious draughts around skirting boards but one area might be the spots in the lean to roof, l’m not sure how well they are sealed.

Charlie-Bravo · 06-01-2021 12:24am

What may be useful is to get thermal imaging done first to identify potential cold spots on reveals of rooflights rather than just through the roof lights themselves.

But I'd agreed that replacing roof lights would be beneficial, and try go for ones with a decent low u-value, before 1.0 anyway.

When you got insulation work done, what type was it? Rigid board between rafters with warmboard to inside, varied ceiling? Mineral wool above flat soffit plasterboard?

Calahonda52 · 06-01-2021 9:26am

Ricey3509 wrote: »

Got a quote of €3100 to replace the 3 , not sure if that’s good ( seems a little high to me?) so l’m hoping to get another quote this week.

No obvious draughts around skirting boards but one area might be the spots in the lean to roof, l’m not sure how well they are sealed.

lets say they are a m sq each, with existing U value of 2.4, proposed 1.0 and 1500 hrs heating hours and oil is 10 cents a kWh, allowing for a bit of carbon tax and a delta T of 20

so the savings per annum are
Value.........area.. T........hrs........cost...W to kW
((2.4-1.0)*(3*1)*20 by 1500)by 0.10/1000 = euro 12.6

Payback is 3100/12.6 = 246 years

IMO get the thermal imaging done as well as some airtightness testing.
Poorly (insulated and airtight) velux are standard issue

Ricey3509 · 06-01-2021 9:34am

Charlie-Bravo wrote: »

What may be useful is to get thermal imaging done first to identify potential cold spots on reveals of rooflights rather than just through the roof lights themselves.

But I'd agreed that replacing roof lights would be beneficial, and try go for ones with a decent low u-value, before 1.0 anyway.

When you got insulation work done, what type was it? Rigid board between rafters with warmboard to inside, varied ceiling? Mineral wool above flat soffit plasterboard?

It was spray foam insulation between the rafters.

Ricey3509 · 06-01-2021 10:24am

Calahonda52 wrote: »

lets say they are a m sq each, with existing U value of 2.4, proposed 1.0 and 1500 hrs heating hours and oil is 10 cents a kWh, allowing for a bit of carbon tax and a delta T of 20

so the savings per annum are
Value.........area.. T........hrs........cost...W to kW
((2.4-1.0)*(3*1)*20 by 1500)by 0.10/1000 = euro 12.6

Payback is 3100/12.6 = 246 years

IMO get the thermal imaging done as well as some airtightness testing.
Poorly (insulated and airtight) velux are standard issue

Hmmm , when you put it like that, perhaps I should just turn up the heating! I'd say there would be an improved 'comfort' level in the room as well with the triple glazing.

If I was getting someone in to do thermal imaging / air tightness testing , I'd imagine it would make sense to get an overall BER assessment at the same time. Anyone got got any recommendations for someone in North Dublin? (PM only)

Calahonda52 · 06-01-2021 11:30am

Ricey3509 wrote: »

Hmmm , when you put it like that, perhaps I should just turn up the heating! I'd say there would be an improved 'comfort' level in the room as well with the triple glazing.

If I was getting someone in to do thermal imaging / air tightness testing , I'd imagine it would make sense to get an overall BER assessment at the same time. Anyone got got any recommendations for someone in North Dublin? (PM only)

Yes, more comfort but I was just showing the math.
No need for the complexity and cost of a BER, at best you may need some heat loss calcs done as well as some TI, A/T testing.
If you followed my math, the rest of the house is easy to do.
I can share a generic blank with you, from SEAI
It might end up costing the same as the BER but you wont be paying for the BER accessors registration and other SEAI related costs of being an accessor and are less lightly to get a generic cut and paste report.

Ricey3509 · 21-01-2021 7:44pm

Borrowed a thermal image camera and the above are the results, looks like its not the Velux that's the main culprit, its the wall the lean to is attached to (so would have been the back wall of the house). I assume there isn't a non invasive way to insulate that?

Worth replacing Velux roof windows

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