Where should I put all this stuff?

[Mr Blobby]

I'm currently trying to allocate space for all the electrics and other plant and need some reassurance and guidance.

 

Its a block cavity passive house on insulated slab and warm roof.  ASHP, UFH, active cooling with fan coils and 8kW pv.  Plans are like this:

 

... with plant originally planned to be housed in 2 plant rooms (each about 3m by 1.2m)  like this:

Room A:  ASHP outside, UVC and buffer tank.

Room B:  MVHR and patch panel/hub etc. ( part to be split into towel store at some point)

 

I had originally anticipated the meter tails would also enter room A and the consumer unit would be in that room, with the inverter outside.  However, the scope has expanded to a hybrid inverter with battery so it can't really go outside any more. 

 

I explained to my M and A consultants that I would prefer to keep the heat generated by the invertor outside the thermal envlope (something they had never heard of before) and so their proposed solution is to run meter tails through a conduit from meter box M under the insulated slab to position C in the garage, where the the inverter and battery and consumer unit would be installed.  While this seemed like a good idea at the time, I am concerned that (i) the garage, being well insulated and more airtight than most commercial houses (and not ventilated by the MVHR) may overheat anyway, and, (ii) having the CU in the garage (which is outside the airtight envelope) may invite trades to penetrate into the garage to access the CU leaving various cable runs through holes in my otherwise airtight plaster.

 

So, having paced up and down scratching my head since yesterday, what do you all think?

 

1. Is the CU in the garage a bad idea for airtightness, or am I overthinking this?

2. Where should I put the inverter / battery / CU? 

3. Running conduit under the slab for meter tails from M to C seems terribly overengineered when I could run the tails into room A, is it over-complicated?

4. Similarly, the M and E proposal to run openreach fibre from P1 to P2 in conduit under the slab goes against my principles of keeping things simple.  Why not go through the wall into the ceiling void?

 

5. Should I move the MVHR into the warm roof and the CU/inverter/battery into room B? 

6. Maybe bring the meter tails into room A and the CU in the boot room next door?

 

With fan coils planned to go in loft above room B for cooling, then maybe that is the right place to avoid invertor overheating ... ?

 

So, where should I put all this stuff?  Should I stick with my M and E advice and leave as is?  All comments welcome. I need all the help I can get.?

 

 

 

[TonyT]

You could put a 100mm duct for electric cables to pass through the garage then seal the duct, the duct being sealed earlier to the vapour barrier.

 

 

 

 

[Mr Punter]

Some thoughts at random:

 

Locating the CU centrally could save some cable.  The fewer the penetrations through your airtight layer, the better.  CU takes very little space.  I tend to locate patch panel, hub, CU and TV / coax in the same place.

 

It will be worth incorporating the MVHR ducting and SVP into the plans as these may need a fair bit of boxing in / risers.  MVHR takes a lot of space and ducting.  If all this is detailed on the plans, your contractors are less likely to just smash holes through where it suits them.

 

You will need a very special door and floor makeup if the garage is to be PH and if you have that, why not just heat it and add it to the conditioned space?

 

I guess your designer has detailed how to avoid the cold bridge junction with the top of the garage wall and the bedrooms above?

 

Not to do with the OP but 2 bathrooms in a big 4 bed house is below what most buyers want so you may want to incorporate future provision for an extra ensuite at the design stage.

 

 

[Mr Blobby]

12 minutes ago, Mr Punter said:

Some thoughts at random:

 

Locating the CU centrally could save some cable.  The fewer the penetrations through your airtight layer, the better.  CU takes very little space.  I tend to locate patch panel, hub, CU and TV / coax in the same place.

 

Centrally together with the other panels feels the right thing to do but does the battery and inverter need to be near to the consumer unit too?  

 

12 minutes ago, Mr Punter said:

It will be worth incorporating the MVHR ducting and SVP into the plans as these may need a fair bit of boxing in / risers.  MVHR takes a lot of space and ducting.  If all this is detailed on the plans, your contractors are less likely to just smash holes through where it suits them.

 

The MVHR ducting, electrics and everything else will be fully specified in the plans before building starts in the spring.

 

12 minutes ago, Mr Punter said:

You will need a very special door and floor makeup if the garage is to be PH and if you have that, why not just heat it and add it to the conditioned space?

 

I guess your designer has detailed how to avoid the cold bridge junction with the top of the garage wall and the bedrooms above?

 

Garage is outside of PH boundary but it will be well insulated.  The garage door will be insulated too but not too airtight.

(I think EVs charge far more efiiciently in a warm garage, but I may be proven wrong ?)

 

12 minutes ago, Mr Punter said:

 

Not to do with the OP but 2 bathrooms in a big 4 bed house is below what most buyers want so you may want to incorporate future provision for an extra ensuite at the design stage.

 

 

 

I agree, but it's nice to be able to build it for us, not the next occupants. 

[Mr Blobby]

51 minutes ago, TonyT said:

You could put a 100mm duct for electric cables to pass through the garage then seal the duct, the duct being sealed earlier to the vapour barrier.

 

 

How would we seal inside the duct?  Silicone?  Foam?

Edited November 12, 2021 by Mr Blobby

[TonyT]

You could do a combination of that.

 

I’ve used Rise Kit’s in the past, that provide a gas tight seal. There are probably some cheaper alternatives too, I haven’t looked for a while

[Mr Blobby]

14 minutes ago, TonyT said:

 

I’ve used Rise Kit’s in the past, that provide a gas tight seal.

 

It took some googling to find it...

 

 

.. what a good idea.  Thank you very much for this.