New Extension Very Cold-Advice Please

Ginger83

Hi all, we have had a new extension built onto an old house and it just seems impossible to heat.I'm wondering if anyone can advise on what to do.

A few points...

Old house is stone. New extension is 24ft by 16ft divided into 3 rooms, 16x16 room, and two 8x8 rooms. Cavity was pumped and 25mm insulated boards put on exterior walls.

However walking from original house into extension is like stepping outside.

dpofloinn

What are you using to heat the space

Ginger83

dpofloinn wrote: »

What are you using to heat the space

Hi we have rads in all rooms run on kerosene but also have a stove. I do find the rooms just wont hold heat, unless the rads are too small.

dpofloinn

Was the oil boiler and stove resized to take on the additional heat requirement

Ginger83

dpofloinn wrote: »

Was the oil boiler and stove resized to take on the additional heat requirement[/QUOTE

They were bought taking into consideration that we were extending.

dpofloinn

What you need to do is calculate the btu's required by your entire house and compare it against your boiler and rads

Ginger83

dpofloinn wrote: »

What you need to do is calculate the btu's required by your entire house and compare it against your boiler and rads

Without sounding stupid how do i go about doing that?

dpofloinn

Just tap in Btu calculator into google and tap in your details, it will ask for things like floor space, number of walls,number of windows etc etc. that will give you the btus required by your house. Then if you measure your rads ( length X height) you can find out their btu for example http://www.quinn-radiators.com/wp-content/uploads/2013/08/PanelBrochure_low-res.pdf. you by can find out the btus of your boilers by googling them by name

Ginger83

dpofloinn wrote: »

Just tap in Btu calculator into google and tap in your details, it will ask for things like floor space, number of walls,number of windows etc etc. that will give you the btus required by your house. Then if you measure your rads ( length X height) you can find out their btu for example http://www.quinn-radiators.com/wp-content/uploads/2013/08/PanelBrochure_low-res.pdf. you by can find out the btus of your boilers by googling them by name

Thank you, i'll work on that and come back with my results.

BryanF

Ginger83 wrote: »

. Cavity was pumped and 25mm insulated boards put on exterior walls..

How's the air-tightness
How are you ventilating

Ginger83

BryanF wrote: »

How's the air-tightness
How are you ventilating

Hi, there are vents in some windows and an extraction fan in a bathroom.

MicktheMan

Ginger83 wrote: »

and 25mm insulated boards put on exterior walls.

Your external walls, more than likely, have no air tight barrier installed, therefore your heat is being lost by convection. Very common issue in new builds nowadays.

What type of lighting on the ceilings of the extension?

listermint

MicktheMan wrote: »

Your external walls, more than likely, have no air tight barrier installed, therefore your heat is being lost by convection. Very common issue in new builds nowadays.

What type of lighting on the ceilings of the extension?

25mm is nothing. Is that even regulation?

MicktheMan

listermint wrote: »

25mm is nothing. Is that even regulation?

My comment has nothing to do with the thickness of the insulation used, or for that matter nothing to do with insulation at all.
I'm questioning if there is an air tight barrier installed.

listermint

MicktheMan wrote: »

My comment has nothing to do with the thickness of the insulation used, or for that matter nothing to do with insulation at all.
I'm questioning if there is an air tight barrier installed.

No use being air tight if the insulation is subpar the two go hand in hand.

One without the other etc etc.

25mm sounds ludicrous tbh

MicktheMan

listermint wrote: »

No use being air tight if the insulation is subpar the two go hand in hand.

One without the other etc etc.

25mm sounds ludicrous tbh

Don't agree.
In our relatively mild/windy climate, I would much prefer to be in an air tight appropriately ventilated with subpar insulation house than in a super insulated house with no thought to air tightness.

Now, perhaps we can get back on topic...

Fayre

If you are concerned about whether the builder that did your extension did it properly one thing you could do is get a thermal image done which will show if the cavity is pumped fully or if any gaps have been left.
I got this done as I have a 6 inch pumped bead cavity, it cost around 200 euro including a report. In my case it showed no cold spots. I think it would be worth it as there's something wrong here

Metric Tensor

I think there's something more going on here. Assuming the pumped cavity is 100mm which you'd imagine it must be then there is a respectable (albeit less than ideal) level of insulation in the walls. I agree with Mick about poor air-tightness being a leading factor but the level of heat loss being discussed here is (in my opinion) too high for just "draughtiness"

OP - what type of roof do you have and what insulation is in it?

Do the radiators get properly hot when the boiler is on? How long can you leave your hand on them for?

Ginger83

MicktheMan wrote: »

Your external walls, more than likely, have no air tight barrier installed, therefore your heat is being lost by convection. Very common issue in new builds nowadays.

What type of lighting on the ceilings of the extension?

Hi just normal white light fitting holding 1 bulb until we decide what to put in place of it.

Ginger83

MicktheMan wrote: »

My comment has nothing to do with the thickness of the insulation used, or for that matter nothing to do with insulation at all.
I'm questioning if there is an air tight barrier installed.

I'm not sure I understand. I watched it being built. 3 outside walls built in 2 leafs of 4 inch blocks, pumped cavity with beads.

25mm insulated slabs on inside of these 3 walls.

4 inch stud partitions inside to divide into 3 rooms. These walls were not insulated and just had normal slabs fitted.

Ginger83

listermint wrote: »

No use being air tight if the insulation is subpar the two go hand in hand.

One without the other etc etc.

25mm sounds ludicrous tbh

Hi, I wasn't really given a choice. I assumed it was fine/standard.

Metric Tensor

The slabbing the inside of an external wall without some sort of air-tightness membrane or detail between the slabbing and the blockwork is a particularly poor detail when it comes to air-tightness.

As I said though - I think there might be something else going on here.

Ginger83

Metric Tensor wrote: »

I think there's something more going on here. Assuming the pumped cavity is 100mm which you'd imagine it must be then there is a respectable (albeit less than ideal) level of insulation in the walls. I agree with Mick about poor air-tightness being a leading factor but the level of heat loss being discussed here is (in my opinion) too high for just "draughtiness"

OP - what type of roof do you have and what insulation is in it?

Do the radiators get properly hot when the boiler is on? How long can you leave your hand on them for?

Insulation went into the floor and 5 or 6 inch thick sheets of insulation went on roof with a rubber membrane cover.

The rads get hot but i thought previously they looked small for the rooms. I'll measure them and come back to you

Ginger83

Metric Tensor wrote: »

The slabbing the inside of an external wall without some sort of air-tightness membrane or detail between the slabbing and the blockwork is a particularly poor detail when it comes to air-tightness.

As I said though - I think there might be something else going on here.

What should be between the slab and the block wall?

Ginger83

Fayre wrote: »

If you are concerned about whether the builder that did your extension did it properly one thing you could do is get a thermal image done which will show if the cavity is pumped fully or if any gaps have been left.
I got this done as I have a 6 inch pumped bead cavity, it cost around 200 euro including a report. In my case it showed no cold spots. I think it would be worth it as there's something wrong here

yes we may have to do that. i cant understand the main house is grand and to go in there its like stepping outside.

Fayre

Ginger83 wrote: »

Fayre wrote: »

If you are concerned about whether the builder that did your extension did it properly one thing you could do is get a thermal image done which will show if the cavity is pumped fully or if any gaps have been left.
I got this done as I have a 6 inch pumped bead cavity, it cost around 200 euro including a report. In my case it showed no cold spots. I think it would be worth it as there's something wrong here

yes we may have to do that. i cant understand the main house is grand and to go in there its like stepping outside.

Sorry just checked there and it was 150 in total. I'll PM you the name of who did mine.

Penn

You've talked about the insulation in the walls but what about the roof and floor? Do you have a specification on what insulation was used there?

Ginger83

Penn wrote: »

You've talked about the insulation in the walls but what about the roof and floor? Do you have a specification on what insulation was used there?

There was 6 inch insulation in floor and 5 inch on roof. Quinntherm 8x4 sheets of insulation.

beauf

Be curious to find out what you find out, when do find the problem.

Ginger83

beauf wrote: »

Be curious to find out what you find out, when do find the problem.

Theres something wrong somewhere because the main house has no floor insulation but its always a comfy room, its also open plan, 38ft by about 14ft.

beauf

Are the inside walls noticeabler colder to touch anywhere in the extension.

Ginger83

beauf wrote: »

Are the inside walls noticeabler colder to touch anywhere in the extension.

The inside of the exterior walls are cold to the touch.

Ginger83

Just something i noticed. The bathroom is 8 foot by 8.5 foot, 1 window and an extraction fan.

The rad in this room is 500mm high by 600mm wide single convector.

Is this big enough for this room?

beauf

I think a small radiator will cause the space to heat up slowly. What your describing sounds like a failure of air barrier and or insulation. It loses heat faster than it can retain it.

I'd also check there is no draught from around the windows edges, or seals, or indeed anywhere. Same with doors or around skirting boards. Are there any vents, and do they have baffles.

Metric Tensor

Ginger83 wrote: »

What should be between the slab and the block wall?

An air-tightness barrier of some sort. Be it a wet plaster finish or a membrane.

I don't think slabbing external walls is a good idea in the current building climate. It can hide all manner of problems.

beauf

I think we have a culture of very poor workmanship in the building sector. Poor air tightness is a consequence.

Ginger83

The bedroom is 16ft by 16ft and has 1 rad 1600mm by 400mm double convector.

I dont want to get on to the builder without having my facts right but this was purpose built as a disabled wing and cold has a big effect on my condition. I cant really use it until i get to the bottom of the problem.

beauf

I think a thermal scan sounds like the first port of call. I would not expect the walls to be cold to the touch as you describe. Sounds like you have external cold air hitting the back of your plaster.

MicktheMan

Ginger83 wrote: »

I'm not sure I understand. I watched it being built. 3 outside walls built in 2 leafs of 4 inch blocks, pumped cavity with beads.

25mm insulated slabs on inside of these 3 walls.

Your inner leaf block wall is allowing any amount of air to pass through to/from the cavity because there is no air tight barrier present in your walls. This, combined with possibly undersized rads may very well be your issue.
I would recommend you get an air tight test done at the same time as a thermal imaging scan to get to the bottom of it and take it from there.

Ginger83

MicktheMan wrote: »

Your inner leaf block wall is allowing any amount of air to pass through to/from the cavity because there is no air tight barrier present in your walls. This, combined with possibly undersized rads may very well be your issue.
I would recommend you get an air tight test done at the same time as a thermal imaging scan to get to the bottom of it and take it from there.

I will look into that. Are these tests expensive to get done?
Its very annoying. I mistakenly assumed all was ok when i seen the insulation that was used.

If its below par what can i do to improve things?

Fayre

Ginger as I said before the thermal imaging cost me 150 in total and that was the total price for a big 2 storey 3200 sq ft house, so no it's not expensive at all.
And an air tightness test for an extension wouldn't be expensive either. There are loads of companies doing it now. Where are you located and we can make some suggestions.
Did you take photos throughout the build? Do you have a photo of the floor before the concrete was poured showing the insulation? Do you have photos of the walls as they were being built? Do you have photos of the roof as it was being built? If you have any photos at all throw them up here and people can see if the problem is jumping out

JonathonS

Ginger, you have a host of suggestions above, the cause of the problem could be one or more, or even none of them. You should get an architect to examine the work and assess what needs to be done. Ideally one with experience of extensions and up to speed on air tightness.