Ball park 137m2 build cost

[SteamyTea]

10 hours ago, Dan1983 said:

concerned about hot water temps with the ASHP as heard they can be on the lower side

From whom.

It seems to be one of those zombie myths that will just not die.

[BotusBuild]

For reference - at 60C you can receive 3rd degree burns in about 5 secs. That comes down to 10 minutes if the water temperature is at 49C. So a lower water temperature makes for a safer home for vulnerable people (elderly, infirm, children etc..)

 

http://www.antiscald.com/index.php?route=information/information&information_id=15

[IanR]

I believe there will be an update to Part L building regs at the end of this year requiring a maximum flow temperature of 55 degrees, so that all new build hot water and heating systems are "designed" for renewables.

[Ralph]

22 minutes ago, IanR said:

I believe there will be an update to Part L building regs at the end of this year requiring a maximum flow temperature of 55 degrees, so that all new build hot water and heating systems are "designed" for renewables.

How does that fit with legionella advice of a 60 degree temp?

[ProDave]

7 minutes ago, Ralph said:

How does that fit with legionella advice of a 60 degree temp?

This Legionella ting is really only a thing if you have private (not mains) water, and the hot water is stored in a vented tank.  Treated mains water and an unvented of water tank and there really is no risk.

 

In any event this reg does not stop you storing very hot water, it just requires the fitting of a thermal mixing valve to blend the very hot water with some cold water to deliver the correct temperature to the tank.

[IanR]

9 minutes ago, Ralph said:

How does that fit with legionella advice of a 60 degree temp?

 

Any low temp systems needs to run a "legionella" cycle every 14 days to lift the temp to 60°

[IanR]

2 minutes ago, ProDave said:

In any event this reg does not stop you storing very hot water, it just requires the fitting of a thermal mixing valve to blend the very hot water with some cold water to deliver the correct temperature to the tank.

 

Is that your interpretation of the new regs?

 

The change is supposedly to lower CO² by 33% from current standards

It's not going to work if you just have to design the system to be low temp, but can still run it as high temp.

[Ralph]

1 minute ago, IanR said:

 

Is that your interpretation of the new regs?

 

The change is supposedly to lower CO² by 33% from current standards

It's not going to work if you just have to design the system to be low temp, but can still run it as high temp.

That's kind of what I was getting at. 

[Dan1983]

I read about the hot water temps on here.

Either way was going to push budget over so was a no go for now 

[Dan1983]

14 hours ago, IanR said:

 

RHI would pay for the ASHP.   It's worth considering, yours is an ideal build. If you are already going with UFH, then it's a decision you can make later in the build, although putting an insulated twin pipe duct in from where you would site the ASHP to the area of the Hot Water Cylinder would be beneficial, while your ground works are being done.

 

That sounds good but take it I still have the initial outlay of the ASHP set up?

I would really like a HP set up if possible 

I take it no issues with house temps in the winter etc?

 

We are having UFH downstairs and rads upstairs/ 2 bathrooms 

Edited May 17, 2021 by Dan1983

[Dan1983]

[IanR]

42 minutes ago, Dan1983 said:

 

That sounds good but take it I still have the initial outlay of the ASHP set up?

I would really like a HP set up if possible 

I take it no issues with house temps in the winter etc?

 

We are having UFH downstairs and rads upstairs/ 2 bathrooms 

 

Yes, you have to fund the Install and you then get the money back over 7 years, index linked. So, you could add it on to your borrowing, if you're not already on the max the banks will lend.

 

A correctly sized ASHP will not lead to any temperature issues with either the house or the water. The better the insulation and airtightness, the smaller HP you'd require.

 

UFH is perfect for the lower temps of an ASHP, ideally under 35 degrees flow temperature for maximum efficiency of the HP. If you are using rads upstairs then they would need to be sized larger than they would for a fossil fuel heated house. You would also need to have a HW Cylinder, and it would need to be larger than fossil fuel heated one again as the temp will be around 50 degrees rather than 60 to 65.

 

From 2022, building regs will require new builds to be designed for low temp (under 55 degrees) systems anyway, in order for them to be future proof and require no retro-fitting for when the 2025 Future Homes Standard comes in and heating systems in New Builds will have to be low-carbon. Even if you don't fit an ASHP now, it would be wise to ensure one could be fitted in the future without replacing all the heat emitters and trying to squeeze in a cylinder where one wasn't planned for.

BTW, redo the RHI calc with a higher SCOP. It's really worth getting your flow temp down and having a higher COP ASHP, something over 4 if possible.

[Dan1983]

I will have a look back over the figures with the builder.

It seems to be difficult to get a figure for ASHP vs System boiler etc cost wise

[IanR]

Take everything that is the same, out of the equation.

 

ie. from the price of the ASHP & controls + the extra cost of a 25% larger HWC + say a 90l buffer (just in case you need it) + twin pipe insulated duct of required length, take away the price of the Gas boiler & controls.

 

The install may be a small amount more due to the MCS requirement for RHI, and a bit more copper pipe and brass fittings for the buffer.

[Dan1983]

Thanks for the info Ian

I was struggling to see where the extra 10k  system cost was coming from (was a guess from builder).

As you say the main question is cost over the actual boiler system rather than the ancillaries as you need them regardless for both systems.

Just guess it would come down to how much bigger the upstairs rads would need to be also.

Once you empty the hot water cylinder is back to full and heat time similar to gas or do you just rely on emersion if hot water if required sharpish?

Lastly are the modern units noisy?

It would be located on the kitchen wall (thinking of noise for neighbours also)

 

many thanks  

[Dan1983]

Fingers crossed no surprises in the ground, looks to be decent soil.

As we are in the forest I expected to be on gravel.

 

upload png

 

 

[Dan1983]

 

More footings going in, when marked out in spray paint foot print doesn’t look that big!

 

[markc]

Thats rather neat excavation. footings always look tiny and cause panic. Its not untill walls go up that a buildings size becomes apparent

[Ralph]

On 21/05/2021 at 10:08, Dan1983 said:

More footings going in, when marked out in spray paint foot print doesn’t look that big!

A family member was convinced that we had dramatically increased the footprint after seeing the footings then coming back to see the kit up. It's very deceptive.

[Dan1983]

I did get the tape measure out to double check!

Concrete being poured today, well that was the plan, hopefully the weather won’t change that.

 

Still trying to decide if we push the budget and use flush casement windows and explore the ASHP route.

[Dan1983]

Edited May 26, 2021 by Dan1983

[Dan1983]

image hosters

[Big Jimbo]

Photo's are very deceptive. That garage base looks like a good size.

[Dan1983]

Garage in 7m x 6m so hopefully big enough for a half height two post car lift and a man cave!

[Dan1983]