Self Build Timberframe in Nottinghamshire

[surcalation]

Hi folks,

 

Currently in the foundation and site preparation stage of a timber frame build. However we can't decide what to do with heating and cooling the house. So far we are having solar pv on house roof and garage roof as they are both SE facing so we will have a 10kw system. We are then going to have 3/4 of the downstairs as UFH and a log burner in the living room. In the bathrooms and en-suite's we are going to have some electric towel rails and then we were going to use an ASHP to make sure the air circulated around the house. 

 

So the problem we are having is that there is no heating per say upstairs other than the towel rails in the bathrooms. When we started the timber frame journey the above set up from several timber frame companies said it was fine to do it that way. But now as we get close to booking trades in firms are questioning the lack of heating upstairs. I currently don't have the design SAP as we are having issues get a PSI value for the thermal bridging. Timberframe company don't have it so our architect is trying to sort it. The u-value for our walls is 0.2 if that helps. 

 

So should we be looking at an UFH heating for upstairs in the bedrooms? Do we need a MVHR?

01 Elevation layout Architect drawing.pdf

[Gone West]

55 minutes ago, surcalation said:

 and then we were going to use an ASHP to make sure the air circulated around the house. 

 

Welcome to the forum. I guess you mean MVHR, not ASHP. That's a lot of PV so do you mean ASHP for heating as well as MVHR for ventilation. Without knowing heat loss and airtightness it's difficult to say about heating upstairs but my guess is with wall U factor 0.2 you would need heating upstairs.

[surcalation]

Cheers for the reply Peter.

 

Was planning on using ASHP for heating but hadn't thought about putting a MVHR in until recently. So maybe with what your saying we should look at UFH heating upstairs too and running both ground floor and first floor via the ASHP? 

[PeterW]

Welcome...

 

So MVHR will help reduce your heating demand - and provide fresh air - eliminating the need for trickle vents but you have to get the air tightness right !

 

Have you got a full model of the heat demand for the house ..? The DER isn’t a good place to start (sorry..!) as it assumes a lot and isn’t designed to provide anything over a single data point. 

 

There is a decent excel model on @JSHarris website, worth downloading. 

[surcalation]

Thanks Peter, currently downloaded the form and now having a look.

 

Naively could i not just have trickle vents and no MVHR?

[MikeGrahamT21]

If you can do MVHR, do it, as it is far and above any other type of ventilation method.

 

Remember, trickle vents only work on days when there is wind, unless you have a dMEV setup, however this is basically like a poor MVHR which doesn't recover any heat.

[surcalation]

Cheers Mike, back on the MVHR bandwagon then

[MikeGrahamT21]

Just remember to pay maximum attention to airtightness, to ensure as efficient running as possible for the MVHR, its fiddly time consuming detail for sure, but its going to be there doing its job for many years to come, and if you have the opportunity before you get to second fix, get an air test done, to detect any small leaks which aren't obvious, again worth its money in the long run.

[recoveringbuilder]

We are just about to start our self build, it will have underfloor heating downstairs, radiators upstairs, a double sided boiler stove (30kw) will supply to a thermal store tank which will supply all our heating and hot water needs, working with a great company up north who has done all the calculations 

[surcalation]

1 hour ago, Christine Walker said:

We are just about to start our self build, it will have underfloor heating downstairs, radiators upstairs, a double sided boiler stove (30kw) will supply to a thermal store tank which will supply all our heating and hot water needs, working with a great company up north who has done all the calculations 

 

what company is that? Might be worth a gander. Currently looking at Midland Renewables, ASCUS and E-ON for our set up

[Nickfromwales]

2 hours ago, Christine Walker said:

We are just about to start our self build, it will have underfloor heating downstairs, radiators upstairs, a double sided boiler stove (30kw) will supply to a thermal store tank which will supply all our heating and hot water needs, working with a great company up north who has done all the calculations 

That's a whopper of a boiler. 

Are you building to standard BR's or are you airtight with MVHR? 

Dont forget to fit blending valves onto the pumps serving the radiators so you can define the temps arriving there. Nowt worse than red hot radiators. .  Slightly oversize the rads and run them cooler for a nice contolable heat delivery. 

Also, what is the means for dumping excess heat ( boiler failsafe ) ? Dedicated heat loss  rad / other ?

[Nickfromwales]

3 minutes ago, surcalation said:

 

what company is that? Might be worth a gander. Currently looking at Midland Renewables, ASCUS and E-ON for our set up

Hi and welcome. 

With that much PV have you considered an all elecric / PV storage solution ?

Im currently specifying three which are ditching the ASHP, but they are passive standard builds which have / will have proven aircrightness and low energy requirements for space heating.

Note : Space heating and domestic hot water ( DHW ) need addressing separately, so don't overlook that. 

 

When you add up what you can save ditching the ASHP ( and its purchase and installation cost - service - maintenance - ongoing glycol replacement cycles - unit lifetime / longevity ) and then look at the cost of buying, maintaining and running a PV / E10 based system it's not miles apart,  but it is far, far less complex and maintenance intensive and some find that quite an attractive option. 

 

With an ASHP you'll need an unvented hot water cylinder ( UVC ) for DHW so also factor in the cost of your annual G3 service / inspection. You can easily say goodbye to £1200-£1500 over 10 years. Not maintaining that could affect your buildings and contents insurance too, so check with your insurers in the small ( tiny )  print. . 

 

Use the the search engine on here as there is ?loads of top notch, impartial, factual, free information contained within these 4 walls. . 

[surcalation]

Cheers Nick, I have been trying to sift through things on the site via the search engine. SO based on our setup with lots of PV and battery storage how would you tackle things?

[Nickfromwales]

1 minute ago, surcalation said:

Cheers Nick, I have been trying to sift through things on the site via the search engine. SO based on our setup with lots of PV and battery storage how would you tackle things?

Battery storage ?

Spill the beans ! 

[surcalation]

1 minute ago, Nickfromwales said:

Battery storage ?

Spill the beans ! 

 

We have a choice of two different battery storages. Tesla Powerwall 13.5kW battery unit or LG Chem 10kW battery 

 

For example, if we decide you want to go with a 10kWp system then we will almost certainly require an export limitation device (not yet confirmed).  SolarEdge has this device but in order for it to work properly we would have to integrate the LG battery into the SolarEdge system.  The Tesla Battery works separately to the solar controls so having this device would potentially cause conflict between the SolarEdge controls and the Tesla controls. 

[Nickfromwales]

I'm not in touch with the current costs of those two battery storage systems. I'm guessing it's 5 figures? 

My approach would be to store electricity as heat energy, but before this chat even begins, we must know your TER and for it to come to fruition. 

For eg, some TF suppliers will give you a weathertight shell, airtight, and guarantee that it will have no more than 0.6 ACH which is almost as well sealed as a submarine compared to what some hairy arsed builder will knock up, with a fag swinging from his bottom lip, whilst he tells you that "the gaps between the insulation are for air flow". 

Are you aiming for airtight? A big jump from 'draughtproofing' btw  

[surcalation]

4 figures, £6k + VAT for a battery. 

 

No idea what TER is? And struggling to work out my ACH. Is there somewhere simple to do it? Maybe my search terms are too broad.

 

Not aiming for a passive house as we don't have the ££££ for that.

[A_L]

1 hour ago, surcalation said:

No idea what TER is? And struggling to work out my ACH. Is there somewhere simple to do it? Maybe my search terms are too broad.

 

Not aiming for a passive house as we don't have the ££££ for that.

 

TER is 'Target Emmission Rate', the amount of carbon produced in heating a house with the same footprint as yours and with levels of insulation, infiltration and heating system as specified in the building regs. Your house DER, 'Dwelling emission rate' must be less than the TER.

 

You specify an air change per hour rate (ACH). For passivhous it is 0.6ACH@50Pa. I suggest you aim at 1-3ACH@50Pa to make effective use of an MVHR. This is a leakage rate at an elevated pressure, the actual unpressurised uncontrolled (infiltration) rate will be considerably lower, about 1/20th if IIRC.

 

If designed in from the start Passivhous need only be 0% to 20% more expensive.