Is this overkill on Part L?

Saddleview

Hello,
New build hopefully starting end of spring. I'm wondering if the combination of "heating and insulation" that I'm thinking of going with has flaws in it?

Block build bungalow, 150mm cavity board insulation
A2W underfloor heating
MHRV
Airtightness with all the membranes and tapes to aim for 3-4 a.c.h.
Double glazed argon filled upvc windows.

I'm probably missing a renewable, most likely pv to power the MHRV and A2W?

Then is all this overkill?

Thanks in advance

Gumbo

Pretty standard to be honest.
Why or what part do you think is overkill?

mickdw

Nothing above standard there other than considering pv.

Saddleview

kceire wrote: »

Pretty standard to be honest.
Why or what part do you think is overkill?

Would the house be performing so well that the underfloor wouldn't even turn on? ie waste of money?

Metric Tensor

To be honest that's bare minimum for Part L compliance.

Air tightness of 3-4 is quite poor considering what's possible with a little effort and 95% of windows I see going in new houses are triple glazed (as they should be considering the minimal difference in price between double and triple)

sydthebeat

Saddleview wrote: »

Hello,
New build hopefully starting end of spring. I'm wondering if the combination of "heating and insulation" that I'm thinking of going with has flaws in it?

Block build bungalow, 150mm cavity board insulation
A2W underfloor heating
MHRV
Airtightness with all the membranes and tapes to aim for 3-4 a.c.h.
Double glazed argon filled upvc windows.

I'm probably missing a renewable, most likely pv to power the MHRV and A2W?

Then is all this overkill?

Thanks in advance

The heat pump should provide you with enough renewables.

Have you had your preliminary part L assessment carried out? That will answer a lot of these kinds of questions.

sydthebeat

Saddleview wrote: »

Would the house be performing so well that the underfloor wouldn't even turn on? ie waste of money?

If at certified passive levels.... Possibly.

Currently part L standards.... Definitely not.

B-D-P--

Saddleview wrote: »

Would the house be performing so well that the underfloor wouldn't even turn on? ie waste of money?

How do you imagine the heat will get from the heat pump then?

Being honest, your aiming pretty low.
When your building, why not reach for high goals?

What floor insulation are you using?
With the little difference in price, why not go triple glaze?
You should aim for 2/5 or less A/T in my opinion.

Calahonda52

Metric Tensor wrote: »

To be honest that's bare minimum for Part L compliance.

Air tightness of 3-4 is quite poor considering what's possible with a little effort and 95% of windows I see going in new houses are triple glazed (as they should be considering the minimal difference in price between double and triple)

3-4 is simply a crap target with MHVR

What follows is just for illustration.

Suppose, you end with an energy demand of 350kWh/per annum with this spec and more importantly not a great standard of work.
Now suppose, with a bit more work, maybe adding 5% to your budget, you get down to 35 kWh/pa

When you do the LCCA
https://en.wikipedia.org/wiki/Life-cycle_cost_analysis
clearly the math will show that the 5% investment will pay for itself in spades, especially with a carbon tax of 200 euros a tonne heading our way, once the EU start fining us billions for our ruminating cows etc:D
.

Saddleview

Calahonda52 wrote: »

3-4 is simply a crap target with MHVR

What follows is just for illustration.

Suppose, you end with an energy demand of 350kWh/per annum with this spec and more importantly not a great standard of work.
Now suppose, with a bit more work, maybe adding 5% to your budget, you get down to 35 kWh/pa

When you do the LCCA
https://en.wikipedia.org/wiki/Life-cycle_cost_analysis
clearly the math will show that the 5% investment will pay for itself in spades, especially with a carbon tax of 200 euros a tonne heading our way, once the EU start fining us billions for our ruminating cows etc:D
.

Would that be a 5% increase in the whole build budget or the budget I've allowed for part L?

mickdw

I'd says far in excess of 5 percent of total build cost.

Calahonda52

mickdw wrote: »

I'd says far in excess of 5 percent of total build cost.

Yes I agree, perhaps 12-15% if done from the very initial design stage and maintained right through the project, however the LCCA issue is what needs highlighting here, especially with the Carbon tax, which now make NPV calculations much more important.