Insulation on Existing Floors linked to New Extensions

[slridg]

Hi guys, would be delighted to hear back on whether I it would be prudent to include insulation on the "original" floors of a renovation.  Architect has not included any for these parts as it will not be checked by building control.  With c/h pipes laid on top of the original concrete 100mm floors it will involve cutting the insulation around the pipework and in some places burying the pipework in the ground to facilitate the insulation. Currently considering NOT to include insulation.

 

Newly Built Ground Floor Extension Areas (these will be checked by building control)

 

Planning on using 75mm Kingspan K3 insulation on newly built front and rear extension ground floors with 20mm insulation turned up at edge on 1200 guage polyethlene d.p.m. with 40mm isocrete flow screed which is being linked through with d.p.c. on 100mm thick concrete floor (original floors of building).  Need to achieve 0.22u value.  Have 115mm build up available = 40mm flow screed and 75mm Kingspan K3.

 

Original Floor Areas

 

I have 70mm build up (excluding floor coverings) available on the 100mm concrete floor.  There are radiator pipes sitting on this 100mm concrete floor with some of the connection pipes rising to 30-40mm in height.  Thinking of putting 30mm Kingspan K3 insulation on top of this 100mm thick concrete floor and then using 40mm flow screed which will link through to the new parts of the building.

 

1. How effective will 30mm K3 be overall in terms of insulation? 

2. Will the flow screed work well with this amount of insulation?

3. Is isocrete flow screed the best route to take (i.e. has a lower build up requirement than sand and cement which fit better with my build up limits)

 

Any comments most welcome - many thanks in advance.

 

 

 

[Ferdinand]

WElcome to the forum, @slridg.

 

Roughly, UFH with basic Building Regs insulation levels is quite sub-optimal, and with no insulation at all .. or imo cutting pipes into already minimal insution ... would be a USA 1970s style of mad, as you lose much of your expensive heat through the floor. 30mm is not a lot of insulation, and I think as it is a whole thermal element unless it is completely floating you will need to comply with Regs, or do it so as a separate exercise perhaps before BC arrives or after they have gone. 

 

I think that given the size of the project, a careful reconsideration of heating strategy may be appropriate to get something good enough for the overall enterprise.

 

WIth those minimal heights available I think, if you are going ufh, you need to consider using a thin ufh system that fits into 18mm, and a laminate or similar floor, rather than screed and tiles. I think even 40mm is very tight for ufh. Are your door heights generous?

 

For UFH I would be wanting a minimum of 100mm of Kingspan or equivalent  and that would perhaps not be enough to make me happy.

 

I think you would be best to take a step back at this stage now that you are well underway, and do some thermal analysis of your completed house .. also taking into consideration what is happening upstairs i.e. Ufh, rads or what? IT may be that digging up those floors is a beneficial option. And what is your planned heat source?

 

My house is very similar to your project ... double fronted 800sqft bungalow taken up to 2100 sqft with a new storey, though renovated by someone else. One issue will be your control system for upstairs vs downstairs on a relatively low spec build, and how to stop it being f%:;()£&g complicated. I have oversized rads upstairs and ufh downstairs, a BFO Combi Boiler, and two entirely separate control systems. Functional, but not ideal.

 

For here, a plan or two, elevations, cross-sections,, a couple of pics and a rough location would help the thread and the feedback. You would be more than welcome to come and visit me if you are near Notts. I would also recommend that you visit someone with a similar build but a simpler heating system.

 

You can get a thermal modelling spreadsheet from @JSHarris' blog, linked from his signature.

 

Ferdinand

Edited January 2, 2019 by Ferdinand

[Jeremy Harris]

14 minutes ago, Ferdinand said:

 

You can get a thermal modelling spreadsheet from @JSHarris' blog, linked from his signature.

 

 

For some reason I can't get the spreadsheet download to work from the blog any more, not sure why, but something seems to have gone awry with the Wordpress  database and is beyond my ability to fix.

 

However, the heat loss spreadsheet is here: Heat loss calculator - Master.txt

 

Just change the file suffix from .txt to .xls after downloading it (the forum has a problem with spreadsheet files as attachments).

 

I also knocked up a UFH calculator that may be helpful: Floor heat loss and UFH calculator.txt

 

Same as the other one, just change the suffix after downloading.

[ProDave]

What will be your finished floor in the original part of the house?

 

If you only have 100mm makeup to play with I would be thinking of 75mm or better still 100mm kingspan with a floating wooden floor on top.

 

Still going to be marginal for UFH.

[scottishjohn]

if you sticking to "thin insulation" better make sure its PIR  --not eps  -far better insulation value

[slridg]

Thank you for your quick response.  The heating is not UFH - I did want a wet floor system initially but had to give up on it due to the restriction of floor levels.  So the heating will be radiators throughout.  Baxi Megaflow System boiler with water tank.  22mm solid wood flooring in non-wet areas on g/f.  Ground Floor Height 2475 and F/F Height is 2345 so no room for reducing heights internally.  

 

I attach some elevations and plans to show the overall scheme.  Also some recent pics showing the radiator pipework.

 

 

01-02-19-Building-Hub.pdf

01-02-19-Building-Hub-Elevations.1.pdf

[Jeremy Harris]

Good move to stick with radiators, as the losses will be a lot lower than with UFH.  UFH is nice, and removes the obstructions that radiators can cause, but it's never as efficient, as there is always some heat loss through the floor, even with pretty good insulation.  We have 300mm of EPS under our slab yet still lose about 8.5% of the heat we put in to the UFH down into the ground under the house.