Internal brick wall insulation

[theredsky]

I love the look of exposed brick walls, and was planning on having a brick feature wall in my extension, created by building one wall with a brick inner skin instead of blocks. However, I am now worried about insulation. The room will have a lot of glazing - 2x large velux, a large apex window and two walls of sliding glass doors - so it's pretty over-glazed, and heat loss and u-values for passing building regs are already concerning me. I have read that brick walls are not as good at keeping in the heat as a block wall with dot and dab plasterboard over the top. I'm now wondering if it would be better to build the wall in blockwork with plasterboard over the top, and then add brick slips at a later date. I'm assuming this will be much better for insulation. The only downside is that fitting the brick slips at a later date will cost more than having the brick wall done as part of the build, be more of a hassle and presumably not look quite as good.

So, I guess my question is, will an internal brick wall be significantly less thermally efficient than blocks plus plasterboard - will it make the room cold? If so, would adding more insulation bring the wall up to the same standard as blocks plus plasterboard? The builder is currently planning to use 100mm insulation.

Any thoughts and advice gratefully received, as the build is due to start in a couple of weeks and I really need to make a decision! Thank you

 

[cdbe]

Just compensate by using a thicker/higher performance insulation in the cavity, eg dritherm 32. Knauf have a calculator on their website but it doesn't seem to include brick on inner and outer skins but I'm sure you could work out manually, or just contact their tech department with your proposal and they'll do a calculation for BC.

 

[Dereekoo]

Checkout this calculator U-value calculator – CBA Block (cba-blocks.org.uk)

 

[Swwils]

How will you ensure airtightness in this new arrangement? Losing the plasterboard and blocks can be significant, especially if the cavity size is constrained. Your proposed constriction of brick/100mm insulation/brick might be about 0.33W/m2K.

Part L limits the total area of openings or glazed elements, such as windows, roof windows and doors, to a maximum of 25 per cent of the extension’s floor area. Which you might go over and be categorized as a "over-glazed extension".

Stuff like this can still pass L1B regulation using one of the alternative methods set out in the document though.

First thing to do is deduct the total area of any windows or doors that, as a result of the extension works, no longer exist or are no longer exposed. Then demonstrate that the proposed extension is no less compliant than if an extension of the same size and shape was built according to the 25% limit. This means increasing the thermal resistance of the walls, floor, roof, or glazing elements above the default values in order to compensate for the increase the area of glass.

If the construction is standard; walls, floors and roof should all be in the range 0.16-0.28W/m2K, there is not much you can do to significantly improve these really - heat losses though the glazing should be significant and as notionally they are 1.6-1.8W/m2K. High-performance, gas-filled, low-e-coated stuff could get you to 0.9 or better - which is effectively what you can need for 40% glazing, but it might not make up for the brick wall.

 

[theredsky]

Thanks, everyone, for your replies.
Swwils - thanks very much for all the helpful info. I'm getting a SAP calculation done because of all the glass, and have now decided to go with blocks/plasterboard/brick slips, as it seems unwise to add to the heat loss issues with a brick wall. Thanks again