Attic conversion what we did

Tim Robbins

I am just posting this here as it might be of use to others.
Background we bought a semi detached house with a BER of B1 and wanted to do an attic conversion. The first fear was losing the B1 BER. I contacted Sustainable Energy Ireland and they told me that as long as the attic was not habitable the BER of B1 stays intact - kinda shows another flaw with the BER!

Anyway, the attic was floored but we wanted to convert it. We were told this makes it much cheaper to convert from estate agent but it still costs a fair few yo yo yos. We got three quotes of 11K and then two more just shy of 15K (excluding vat). The 15K came with recommended builder and was a better spec so we went with that.

The insulation spec was driven by recommendations we got from Kingspan.
On the roof, I put Kingspan Thermapitch TP10 150mm and Kingspan TW 56 37.5mm (25mm insulation, 12.5mm plasterboard). According to Kingpsan My U-Value for roof is: 0.16 per square metre.

On the external gable we used: 102.5 kooltherm k18. Again according to Kingspan U-Value here is 0.20.

And on the internal gable (which was very small as the stairwell was there) we used a mixture of what was leftover. On the stairwell we just used sand cement and a plaster coat. The reason for this was that, sand cement was the only thing there on the other floors on the interior gable at the stairwell so we stayed consistent.

We have two Velux windows: P10. U Value 1.3.

Cost for architect drawing, structural engineer advise and build was just shy of 15K. Painting and carpetting another 2K.

One thing that has been a disappointment is I expected the room to be really warm but it is not. Why? Because we have 300MM rockwool above our bedrooms which means when the roofs of our bedroom are about 17 degrees the floors of our attic are about 12 degree c.

Also the interior gable wall at stairwell is usually colder than the exterior gable wall. I can get temperatures of 10 degrees on the interior wall at stairwell to attic, where interior wall to 1st floor will be 16 degrees at 1st floor.

However, this does not completely scare me as the windows come in at about 9 degrees.

Note: the temperatures are only guidelines. I took them with this toy

If I had the rad's on at different strengths etc I'd obviously get different temperatures. But these temps were really just to show me differentials mainly between the floor of the attic (which we found cold) and the other parts of the attic.

heavydawson

Tim Robbins wrote: »

I am just posting this here as it might be of use to others.
Background we bought a semi detached house with a BER of B1 and wanted to do an attic conversion. The first fear was losing the B1 BER. I contacted Sustainable Energy Ireland and they told me that as long as the attic was not habitable the BER of B1 stays intact - kinda shows another flaw with the BER!

Anyway, the attic was floored but we wanted to convert it. We were told this makes it much cheaper to convert from estate agent but it still costs a fair few yo yo yos. We got three quotes of 11K and then two more just shy of 15K (excluding vat). The 15K came with recommended builder and was a better spec so we went with that.

The insulation spec was driven by recommendations we got from Kingspan.
On the roof, I put Kingspan Thermapitch TP10 150mm and Kingspan TW 56 37.5mm (25mm insulation, 12.5mm plasterboard). According to Kingpsan My U-Value for roof is: 0.16 per square metre.

On the external gable we used: 102.5 kooltherm k18. Again according to Kingspan U-Value here is 0.20.

And on the internal gable (which was very small as the stairwell was there) we used a mixture of what was leftover. On the stairwell we just used sand cement and a plaster coat. The reason for this was that, sand cement was the only thing there on the other floors on the interior gable at the stairwell so we stayed consistent.

We have two Velux windows: P10. U Value 1.3.

Cost for architect drawing, structural engineer advise and build was just shy of 15K. Painting and carpetting another 2K.

One thing that has been a disappointment is I expected the room to be really warm but it is not. Why? Because we have 300MM rockwool above our bedrooms which means when the roofs of our bedroom are about 17 degrees the floors of our attic are about 12 degree c.

Also the interior gable wall at stairwell is usually colder than the exterior gable wall. I can get temperatures of 10 degrees on the interior wall at stairwell to attic, where interior wall to 1st floor will be 16 degrees at 1st floor.

However, this does not completely scare me as the windows come in at about 9 degrees.

Note: the temperatures are only guidelines. I took them with this toy

If I had the rad's on at different strengths etc I'd obviously get different temperatures. But these temps were really just to show me differentials mainly between the floor of the attic (which we found cold) and the other parts of the attic.

You're not really meant to have 2 layers of insulation at any part of your house. Insulation either between joists or between rafters but not both. Sounds like you were relying on heat escaping from downstairs to heat the upstairs? Is there any heat source in the attic? Gravity is going against you getting a rad up there, but an electric heater might be an option? Obviously, fire regs are a must-read in this area.

Tim Robbins

heavydawson wrote: »

You're not really meant to have 2 layers of insulation at any part of your house. Insulation either between joists or between rafters but not both. Sounds like you were relying on heat escaping from downstairs to heat the upstairs? Is there any heat source in the attic? Gravity is going against you getting a rad up there, but an electric heater might be an option? Obviously, fire regs are a must-read in this area.

We have one rad up here.

Kingspan told me to have the two layers. The 150MM is in between rafters which are 220 mm. The 37.5 MM is 12.5 mm plaster board and sits over the rafters.

Why is that bad?

Myrddin

Tim Robbins wrote: »

We have one rad up here.

Kingspan told me to have the two layers. The 150MM is in between rafters which are 220 mm. The 37.5 MM is 12.5 mm plaster board and sits over the rafters.

Why is that bad?

I think he means you have insulation between the floor joists, & also between the rafters. The stuff between the floor joists is preventing heat rising up to the attic where it can be then trapped by the rafter insulation

Tim Robbins

EnterNow wrote: »

I think he means you have insulation between the floor joists, & also between the rafters. The stuff between the floor joists is preventing heat rising up to the attic where it can be then trapped by the rafter insulation

Absolutely. But taking it up means bye bye BER.
We also have an airtight sheet there. I wouldn't do it unless an insulation expert could guarentee me we would keep B1.

air

Since you know your projected U-value for all of the walls / floors and their areas you should be able to calculate your heat load at a given outside temp easily. Have you done this and compared it with the output from your single radiator?
How have you treated the ceiling or is the roof vaulted?
A few before and after pics would be nice if you don't mind putting them up.

sydthebeat

Tim Robbins wrote: »

Absolutely. But taking it up means bye bye BER.
We also have an airtight sheet there. I wouldn't do it unless an insulation expert could guarentee me we would keep B1.

Firstly, the attic conversion by definition will affect your BER, once its served by a fixed stairs. The floor area of the house is now larger. You also have new heat loss elements namely the dormer stud walls, the sloped roof, the gables and the flat section over the conversion.

secondly, the floor between the habitable section of the attic and the first floor is no longer a heat loss element so removing the insulation at this area doesnt affect the BER. I personally wouldnt do it though, i would just pin point how and why you are loosing heat in the attic. Personally i would suggest that air tightness has a lot to do with it. On a windy day is it very hard to heat this space?

Tim Robbins

sydthebeat wrote: »

Firstly, the attic conversion by definition will affect your BER, once its served by a fixed stairs. The floor area of the house is now larger. You also have new heat loss elements namely the dormer stud walls, the sloped roof, the gables and the flat section over the conversion.

secondly, the floor between the habitable section of the attic and the first floor is no longer a heat loss element so removing the insulation at this area doesnt affect the BER. I personally wouldnt do it though, i would just pin point how and why you are loosing heat in the attic. Personally i would suggest that air tightness has a lot to do with it. On a windy day is it very hard to heat this space?

The area of the house is not larger as technically the attic conversion is storage space as it is not habitable technially. We don't have enough of it at height 2.4 M. I'll dig up email from SEAI and post up.

I think air tightness is pretty good. I went around with my infra red gun and couldn't find cold spots. If you can imagine where the sloping ceiling meets the wall that is only 1M high (is there a technical name for this wall), well we carried the roof insulation back behind this wall for about another 1M and then dropped it to meet the rock wool.

If you walk to the very edge of a bedroom beside the window and look above you, the rock will is needed here as the roof insulation in the attic does not go to the very very edge of the roof.

I don't think we are loosing heat in attic it more a case it is cold because it is not getting any heat from 1st floor. So when we go up it is cold but heats up quickly. We only put one rad in, probably should have put two in.

And we don't use as much as 1st floor so we don't have the heat on there that much.



I will do more measurements and post up.

Tim Robbins

air wrote: »

Since you know your projected U-value for all of the walls / floors and their areas you should be able to calculate your heat load at a given outside temp easily. Have you done this and compared it with the output from your single radiator?

I am not sure how to do this or compare it with output from single rad.

How have you treated the ceiling or is the roof vaulted?

Again, sorry I don't know enough to answer this. If you can explain or post link that would be great.

A few before and after pics would be nice if you don't mind putting them up.

Will root around.

heavydawson

EnterNow wrote: »

I think he means you have insulation between the floor joists, & also between the rafters. The stuff between the floor joists is preventing heat rising up to the attic where it can be then trapped by the rafter insulation

Yup, I do. To be fair TR, I wasn't implying that it was was a poor job or anything, so my bad if it came across like that. From going through our own self-build, I know our own engineer stressed the building envelope as being the primary consideration for insulation and air-tightness. So a single continuous layer running all around the habitable area.
This is a design principle, and in the real-world is not always practical especially where conversions are involved (or so I imagine).

How have you dealt with things like condensation / ventilation in that space? One of the earlier posters mentioned that air-tightness could be a source of heat-loss up there.

air

To me it doesn't sound like there is any problem with the room at all.
The fact that Tim says it heats up quickly (even with just one rad) seems to imply that the room isn't in fact losing much heat.
As I see it Tim's only issue is that the room isn't warm without heat on, which is simply a result of the good insulation between the floor below and the attic.

Switching to a double radiator should improve the heat up times up there (assuming boiler can cope), or you could just leave the door up to the room ajar if you want it to be a bit warmer on an ongoing basis.

By a vaulted ceiling I meant does it have joists above you in the attic space - based on your 2.4m comment I suspect it does. I was asking what kind of insulation you have above the attic ceiling (the horizontal part of it).
In any case I think it's moot!

heavydawson

I had a quick look at the tool you used to measure temperature. I'd take it's result with a grain of salt, from one of the reviews:

]
This product s interesting to use to find cold spots etc, but it's quite difficult to "aim". After having used it a few times it was aparent that depending on how far away you are from the surface the sensor could be above or below the coloured dot. Also the unit only tells you the measured surface temperature in relation to the initial reference temp, which in itself is only in relation to ambient temperature, i.e so you can't point at a surface and find out it's actual temperature, so if your sensor was in a room with an ambient temp of 20c and you measured a wall which is 18c the unit will show a refernce temp of -2c. I found it a bit of fun to use but not convinced it helped me to find any real air leaks or cold spots that i could address.

That said, it's quite cheap and I'm rather have one than not. That said, if I could find a cheap one of these, that would be my preference

Tim Robbins

heavydawson wrote: »

That said, it's quite cheap and I'm rather have one than not. That said, if I could find a cheap one of these, that would be my preference

Holy f*ck. What's a lovely tool. It is pity there is nowhere you can rent these.

heavydawson

Tim Robbins wrote: »

Holy f*ck. What's a lovely tool. It is pity there is nowhere you can rent these.

Heh, was thinking I'd buy one and rent it out to posters on the construction forum here on boards.

Tim Robbins

heavydawson wrote: »

Heh, was thinking I'd buy one and rent it out to posters on the construction forum here on boards.

Go on...

heavydawson

Tim Robbins wrote: »

Go on...

Depends on what folks would be willing to pay. If you're like me you'd want it for a couple of days to full inspect the place. 3 days - €100? Or would you want it for longer?

MicktheMan

Tim Robbins wrote: »

It is pity there is nowhere you can rent these.

You can "rent" it with an experienced trained operator, it's called a heat loss survey:)