UFH Design - LoopCAD, Heatpunk,Spreadsheets & Copilot

[Adrock]

Hey everyone, I'm new to this place. I've been lurking for a while so, by way of introduction; I'm an electrician by trade and I decided to undertake a lowerground/basement conversion and extension at my own house with the vast majority of the work being undertaken at weekends. I'm over two years down the road in this journey and I'm at UFH design and pipe installation prior to getting screed down.

 

The extension has access to the garden, all walls aren't underground but the majority of the existing house walls are. I'm going to internally insulating the walls.

 

My floor build up is a 150mm ground bearing reinforced concrete slab, cavity drainage membrane, 100mm PIR insulation, UFH, sand/cement screed.

 

As for heat loss calculations, I've been playing a lot with a few options. My first port of call was heatpunk, I found it intuitive and managed to define all of the different elements I required such as the differing wall build ups. I've also played with the famous Jeremy's heat loss calculator spreadsheet and Copilot. They are all within 10% of each other so I'm confident the heat loss figures look reasonable.

 

That brings me onto LoopCAD, I've struggled with the materials and insulation details to reflect what I have and therefore achieve similar heat loss figures the three methods above have indicated. Hopefully I've managed to put the right figures in and have something approximating a pipe layout. Pipework is 16mm PEX-AL-PEX, I'm sure I saw a recommendation for 20mm, would it make sense to use bigger pipes?

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The area directly above the manifold is the stairs, so I need to tidy up the pipes leaving the small cupboard to get to each room. Have I missed anything obvious? Seeing as this is my first system I'm mindful I might have missed something crucial. The cupboard and hallway are both shown as being too cold but from what I've read on this forum it should be fine considering the circuits are running through the areas.

 

Any observations, comments, feedback would be greatly appreciated.

 

[JohnMo]

1 hour ago, Adrock said:

100mm PIR insulation

First not enough insulation really

 

You either do no insulation and use ground as a heat store, then run heating low and slow for the whole heating season, or at least 150mm PIR, but the more the better. This limits heat seeping downwards never to return.

1 hour ago, Adrock said:

16mm PEX-AL-PEX

Do yourself a favour and swop to Pert-Al-Pert, easier to manipulate. 16mm is the size to use.

 

Flow dT is likely to either 4 or 7 rather than 10.

 

Layout looks good, making use of pipe to and from rooms to heat halls etc.

1 hour ago, Adrock said:

The cupboard and hallway are both shown as being too cold

Easy way to fix that, pull the hall pipes closer together then use a longer pipe length for room A-02 and make an addition loop or two in the hall.

[SteamyTea]

As @JohnMo says, more floor insulation. 

 

Once you know the total, worse case, heat losses, it is relatively easy to work out the pipe spacing.

I cannot think of a good reason to go greater than 16mm tubes. I think 20mm is for very long runs and lots of tight bends.

Check you can do the full loop with one length, you really only want joints at the manifold.

Edited 21 hours ago by SteamyTea

[Adrock]

32 minutes ago, JohnMo said:

First not enough insulation really

 

You either do no insulation and use ground as a heat store, then run heating low and slow for the whole heating season, or at least 150mm PIR, but the more the better. This limits heat seeping downwards never to return.

 

Balls, I'm too far down the track to change that now, I think. I wish I'd ask the question before going off the architects bloody drawings. I should have known, I've already ignored a lot of his other details after researching them myself. Will it have a major impact on the comfort levels of the rooms?

 

I have 75mm screed/floor finish after the original 100mm insulation, not much to play with.

 

32 minutes ago, JohnMo said:

Do yourself a favour and swop to Pert-Al-Pert, easier to manipulate. 16mm is the size to use.

 

Cheers, I'll be ordering that later today.

 

32 minutes ago, JohnMo said:

 

Flow dT is likely to either 4 or 7 rather than 10.

 

I'll make a note of that, does that mainly affect flow rates?

 

32 minutes ago, JohnMo said:

 

Layout looks good, making use of pipe to and from rooms to heat halls etc.

Easy way to fix that, pull the hall pipes closer together then use a longer pipe length for room A-02 and make an addition loop or two in the hall.

 

I've played around with the spacings and layouts and it appears there isn't much difference in performance between 150 and 200mm spacing. Is there a general consensus of what it should be? Looking at LoopCAD, if I change the pipe centres it still performs as required.

 

I've seen the chart with lines to draw between mean water temp and spacings. Seems like what I've drawn so far with 150mm centres is too much. I have a 2734W loss in the space and around 72m2, which works out at 38w/m2. Would it be feasible to install at 150/200mm centres and if its too hot, turn down the flow for the circuit?

[JohnMo]

6 minutes ago, Adrock said:

impact on the comfort levels of the rooms?

No just you wallet as you will loose heat downwards

6 minutes ago, Adrock said:

I'll be ordering that later today.

Be careful with the lengths you order as it can get a lot of waste

 

7 minutes ago, Adrock said:

'll make a note of that, does that mainly affect flow rates?

It affects flow rates and flow temp. UFH output is governed by the mean flow temp, the smaller the dT the lower the flow temp needs to be.

 

9 minutes ago, Adrock said:

I've played around with the spacings and layouts and it appears there isn't much difference in performance between 150 and 200mm spacing. Is there a general consensus of what it should be? Looking at LoopCAD, if I change the pipe centres it still performs as required.

Once you get fairly well insulated the flow temp has very little impact on floor heat output.  What is changes is reaction time, so how long you need to allow for the floor to impact room temp. I have a loose 300mm spacing (but much lower heat loss per m2), it's a glacial time scale from cold floor to hot house, but that only occurs once per year.  Rest of the time its running weather compensation, so only has to react to daily changes in the weather.

 

You can either use 150mm or relax the spacing slightly, but with your heat loss I would stick to 150mm.

 

Is this an add on to an existing system, boiler or heat pump?

[Adrock]

The underfloor heating in this thread is going to be on a boiler until the day I get the entire house upto spec. Its a long term project 😅

 

Its an old pre 1930's house, solid brick walls, that will eventually be externally insulated complete with lots of airtightness improvements and MVHR. But I've started from the bottom and am going to work my way up, once this level is complete the ground level gets a garage conversion and modernisation throughout. I'm looking at the ground level having underfloor heating too.

 

If it all goes wrong I'll just stick massive radiators in 🫣