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Thermal break at threshold?


Vijay

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Without a thermal break, surely the garage floor would just have a full cold bridge to the external ground?

Edited by Nickfromwales
Amended to remove quote / typo
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EPS wrapped in a vermin mesh and then a galv / stainless cattle grid atop, bridging the EPS and supported by both cold and warm slabs for load-bearing (driving over ) ?

Surely this is quite straightforward to resolve :/ ? What about a thermal break in the heated screed / concrete and then only heating 8/10ths of the garage floor? 

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12 hours ago, Vijay said:

It's an attached garage and the floor will be insulated and I'm hoping to have UFH in there too

 

Ooo, sounds good. Keeping the vintage Bentley dry? Ensuring the wine racks are kept at best temperature? Stopping the yoga mediation mat being too cold? Keeping the butter on the pole dancing pole ready for action? Do tell!  Would have loved to have done the same! 

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8 hours ago, Nickfromwales said:

EPS wrapped in a vermin mesh and then a galv / stainless cattle grid atop, bridging the EPS and supported by both cold and warm slabs for load-bearing (driving over ) ?

Surely this is quite straightforward to resolve :/ ? What about a thermal break in the heated screed / concrete and then only heating 8/10ths of the garage floor? 

I did wonder about some sort of cattle grid but didn't think it would look too good. I'll look into that some more :)

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Any grid system will allow airflow into the garage so you will negate the benefit of sealing the door and any heating benefit. 

 

I would also check that under Part L1 you are not causing yourself an issue with BRegs as the whole of the garage will need to be insulated to minimum levels and potentially included in any air tests as it becomes part of the heated envelope of the building. 

 

 

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Ok but insulating it and stopping air infiltration to meet BRegs along with getting the minimum standards etc are all interlinked. 

 

You've said yourself that getting an insulated garage door is easy, getting an air tight one is nigh on impossible. 

 

Whats driving the requirement for a heated garage ..? Costs may far outweigh any benefits on this one

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Oh I see your point now, if they did any air leakage test, the garage would fail miserably. I think a conversation with the BCO may be in order then?

 

Honestly Peter, nothing more than creature comforts as the garage will be my workshop too and something I've dreamed of having for many years.

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If it were me, then I'd officially make the garage an area that's outside the heated envelope, so you don't have to comply with Part L1 for it.  You can then do pretty much what you like with the garage, practically, including fitting UFH and insulating it. 

 

Our new garage is detached, but well-insulated all around, and the insulated Seceuroglide roller door seals pretty well, but not to house-type standards.  It has brush seals along each side and a soft hollow rubber seal at the bottom, that seems to seal pretty well to the concrete threshold.

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Just write "unheated" on the plans?

 

I have an attached garage. There is no mention on the plans of any heating, i am not expecting anyone to insist on insulation levels or air tightness of the garage, but I will be insulating it for my own benefit.

 

Being a single garage under the limit it does not require any specific ventilation provision, though building regs do say in those conditions you should not attempt to achieve a high level of air tightness.

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All plans have already been approved and submitted to BC. There is mention of insulation in the floor but nothing about heating or wall insulation/air tightness at all apart from being built in ICF

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Yes it would kill your SAP calculation.

 

How often do you actually plan to use the garage as a workshop and will you frequently be opening the door to take cars in and out. Surely if so you are going to lose a lot of heat when you open the door.

 

An insulated Hormann double door has a U-value of 1.4. That's going to be like putting a 10 square metre double gazed window in a room, one with poor draught proofing. 

 

The garage is going to have high constant heat losses. In winter the double door will lose around 200W per hour. It is also likely to be a big area. The heat losses from the fabric of the room will be 200W per hour if all of the floor roof and walls are external (assuming 6m x 6m garage) and they have an average U-value of 0.15. It sounds like it is maybe external but attached to the house by one wall.

 

BTW if you are heating it and there is no room above it you'll need to insulate the roof or the heat losses there will be massive.

 

So including air infiltration you are probably looking at 500W/hour to keep the garage warm in winter and a lot more if you open the door, although that will likely depend on the wind direction.

 

Of course a lot of the time it won't need heating when it is warmer outside. So very roughly 12kW/day for half the year, call if 2000kWh. Around £70 a year, not drastic. I'd still be tempted just to run a fan heater when I am actually in there. If it's insulated you won't be heating up from too low a temperature and when you build up a sweet working you can turn off the heat. I find my integral , insulated but unheated garage rarely gets blow 11C no matter how cold it is outside, indeed it stays warmer than the conservatory!

 

Edit - Forgot to mention a fan heater is a lot cheaper than UFH also unless it is already in the slab.

 

Some people will tell you that putting a car in a heated garage will make it rust. Especially if you put a wet salt covered car in the garage in winter. Certainly heat speeds up chemical reactions but it won't be that hot and cars are pretty immune to rust nowadays.

 

BTW I just assumed it's a double garage as it seemed in keeping with the size of your house.

Edited by AliG
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