Best way to insulate bungalow extension

[richo106]

Hi

 

We are in the planning stages of our bungalow extension. we will be adding another floor to our exisiting 1960's bungalow. The foundations are good and suitable for another story. One of my major concerns at the minute is insulation. We are most likely be having a ASHP (no mains gas in area) so its either LPG, Oil or ASHP so aware our insulation needs to be good.

 

Our current bungalow is 2 skin brick with only about an 80mm cavity with blown insulation in it and the plan from the builder is to build straight on top. We are planning to render the bottom (existing half) and then have new brick on top. The problem arises when we only have 80mm cavity. Aware I will need more insulation than this to satisfy BC and use of our ASHP. 

 

Would a solution be to install 25mm (or obviously 50mm) on the inside of the external walls? before fixing the plasterboards. would this work?

 

Would people remove all the existing plaster to get to bare brick? and would they use the warm batten method or just the pir between the battens?

 

We thought about external insulation but we worry this will stick out to much compared the brick

 

We will be have a new concrete base slab with 100mm insulation for UFH and possibly UFH upstairs with the pipes running in the insulated boards (maybe)

 

Any ideas/advice greatly appreciated

Edited October 30, 2021 by richo106

[Mr Punter]

With UFH on the ground floor you needs lots of insulation to prevent the heat escaping.  100mm is not enough, even if it is PIR.  Insulate properly, make it airtight and you will not need UFH upstairs.

[TonyT]

Won’t the building controls drawings advise what you need to achieve as a minimum?

 

I had to put 200mm pir in the walls and floor

[Onoff]

5 hours ago, richo106 said:

We will be have a new concrete base slab with 100mm insulation for UFH

 

With even 300mm of EPS under his slab, a member here with a super insulated house build calculated an 8% heat loss down through the floor. 

 

100mm is not enough. 

[richo106]

Thanks for your comments they are all taken on board.

 

My other question is that exterior insulation has been mentioned with builders etc but the existing bungalow and the new extension does/will have a cavity. The existing cavity is filled with the blown insulation type  I believe at its only 80mm wide. Would exterior insulation be pointless as most of the heat out of the rooms would of been lost in the cavity?

 

Would my best option to internally insulate on the external walls of the house? Was thinking 50mm

 

What is the best way to internally insulate?

 

Thanks again

[Andehh]

I am no longer expert, but insulated / thermal plasterboard is an easy option!

[Marvin]

Hi @richo106

 

We renovated and extended our bungalow.  We have no mains gas.

Originally the bungalow had night storage heaters. We insulated with 200 pir in the floor, 150 in the walls and 400mm fluffy in the loft, improved the air tightness, added a LPG boiler and a MVHR.

Since then we have revised our plans and have replaced the LPG with an ASHP and are adding PV for the electric vehicle and general power.

 

After reflecting on the systems available for us the best synergy for comfort and efficency is the ASHP, MVHR, PV and EV combo. I know others will be different..  

 

Assuming you are not thinking of moving for a long time: In my humble opinion you pay for the building works once, you pay for the heating/cooling costs every year: Consider the thermal resistance of the bungalow very carefully.

 

Lots of people here have learnt the hard way including me. 

 

Best of luck

 

Marvin.

 

P.S. and had I thought (known) about it I would have installed a SunAmp.

 

Edited November 6, 2021 by Marvin
Add P.S.