Heating system - new build

dfader

Hi all,
The usual heating system dilemma -

After having to put off our new build for about 5 years due to the negative equity we have on our 3 bed semi we hope to be able to start later this year.

House is going to reasonably close to passive - 225mm cavity pumped, triple glazed, MVHR, every junction has been carefully detailed to minimise coldbridging, high level of airtightness etc. All detailed and specified.

Initially I’d planned for air to water and underfloor for heating system and hoping to avoid solar panels.

Had a QS price it all up recently and it was over budget, so we went through a cost cutting exercise. One thing he suggested getting rid of concrete first floor in favour of normal timber joists and going the traditional oil and radiator route, probably saving about €5000 in total between the floor and heating system. This is mainly due to the €3700 saved between precast concrete first floor and normal timber joisted first floor.

Not having a concrete first floor doesn’t concern me but am disappointed to have to use oil and solar panels and would mean that we’d also be looking for an airtight boiler stove, which are hard to find and expensive to supplement the oil.

House is already modest (2100 sq ft) and was reduced in size as much as we would want to and is a straight forward two story, so please don’t suggest reducing square footage to save there.

Anyone been through this dilemma and any advice?

MicktheMan

What does "House is going to reasonably close to passive" mean?
Do you know your heat demand / heat load?
Has the design been modeled in phpp?

You may be over complicating the issue without knowing the above.

Also, I don't understand why you need a boiler stove to supplement your oil boiler.

dfader

Mick, Thanks for reply.
It's A2 rated.
Dont think ill model it in PHPP - cost is prohibitive.
I don't need a stove with a back boiler but would want it owing to the uncertainty of oil prices in the future.

Gumbo

5 years with no works. Have you extended you planning permission?

dfader

Yes

Outkast_IRE

Getting rid of the concrete floor on the upper level is a bad decision for numerous reasons.

1. The increased thermal mass of the concrete upper floor will help maintain a stable temperature internally and smooth out the daily diurnal variations in temperature. Its a positive thing in terms of heating and cooling, its win-win, keep this if at all possible.

2. Sound - Concrete upper floors are excellent for soundproofing, no more hearing something banging around etc, anybody who goes from a timber joist house to one with a concrete upper floor really appreciates the noise reduction.

I would not be so concerned about going the oil and radiator route, if the house is built to the standard you are saying then you wont be running it a huge amount each year anyway and when oil prices do go up in the future there is plenty of scope for alternatives.

That being said a €5000 euro saving is not a huge amount in the long run, going with the air source heat pump and underfloor is an investment that will be worth it long run.

MicktheMan

dfader wrote: »

Mick, Thanks for reply.
1. It's A2 rated.
2. Dont think ill model it in PHPP - cost is prohibitive.
3. I don't need a stove with a back boiler but would want it owing to the uncertainty of oil prices in the future.

1. That's not what I asked. A2 rated being reasonably close to passive is like a cow being reasonably close to a small horse. Close in that both have four legs & a tail and are close in size but are completely different animals.
2. But what about the benefit of allowing you to make informed decisions based on accurate data probably saving you multiples of the cost in the process.
3. Oil isn't unique to price uncertainty.

dfader

Thanks for the reply micktheman,


1. At present all i can tell you is the primary energy use at 47 kWhr/m2/annum. House is 195m2.
2. I agree with you about the benefit - I'd love to have PHPP done, but doubt I will be.
3. Oil is not unique to uncertainty but it a sure thing that it will become very expensive in 15-20 years. Sure electricity and other fuels will follow but we would hope that not by the same degree.

Metric Tensor

Personally I would sacrifice other things before the precast first floor. I've found the sound benefits to be huge and there's a solidity to walking on them that (imo) makes the house feel more expensive/impressive. They also give you the benefit of having blockwork walls upstairs thus providing better sound proofing between the bedrooms, en-suites, etc.

I'm surprised that the cost difference between timber joists and hollowcore is so high but I'm not a QS so I'll have to bow to his/her experience on the matter.

Does your pricing include fittings and finishes? Sanitary ware, carpet, tiles, fitted kitchen, etc.? If so there could be massive savings to be made there that would make €3,700 look tiny. Just a suggestion!

Metric Tensor

Apologies - double post.

lownhard

Do not lose the concrete first floor
one of the best decisions I made. Requires careful airtightness detailing but totally worth it.

MENACE2010

Hi
okay , I have been in a similar situation whereby the "wish" and reality came to a head a decisions needed to be made in order to fit budget, first off look at the total build cost . I presume if you are working with a CS you have included everything and the kitchen sink into the budget ?

We applied one method of thinking in our build , the budget spend needs to be on elements in the build that you cannot change or change will be difficult like "swapping out windows for example" , so you have pumped cavity and spend serious time on the detailing of the build ,those will help you later to "afford" the house if that makes sense, you dont want a mortgage + a massive energy bill on top of it .
try to stick with the "frame" of the house , kitchens , furniture will / can change overtime you dont need to spend day 1 tons of money on furniture ( 3 yrs in and we now have proper couch.).

So find other places where you can save money , for example we had Aluclad triple glazing on our budget,. that became PVC triple glazing.. saving of 8% on our build cost . ( that is a lot more saving than 5K over the total build cost for changing the floor) , kitchen what is the kitchen spec and cost ? look around / Shop around .. Finishes ? what is finish specification , what is the electrical installation going to cost . Whiteware where do you get your sanitary.. we got nice ones .. but we stopped at spending a serious money as we don't live in bathroom , all bathroom furniture is this Swedish company ( blue and yellow) again here is where you save money..

you can PM me. if you need more help or suggestions .. don't get disheartened .. you will end up with your house that you had planned but in smaller steps ..

blast06

How much extra does the triple glazing cost versus double glazing ..... and how much per annum would the triple save you in heating over double. At a wild guess, i would be it would take you 40+ years to save back the extra spend on triple glazing (my logic for this wild guess is i have a 2600 sq ft house with a total heating bill for the first 12 months of €392 to keep the house at 20 degrees 24/7 ..... A2 BER). Triple glazing would have cost me an extra €2,800)

MicktheMan

blast06 wrote: »

How much extra does the triple glazing cost versus double glazing ..... and how much per annum would the triple save you in heating over double. At a wild guess, i would be it would take you 40+ years to save back the extra spend on triple glazing (my logic for this wild guess is i have a 2600 sq ft house with a total heating bill for the first 12 months of €392 to keep the house at 20 degrees 24/7 ..... A2 BER). Triple glazing would have cost me an extra €2,800)

While, with your level of heating costs, it may not be economical to go TG, what is often overlooked is the thermal comfort upgrade that good TG windows give over DG windows. This comfort dividend cannot be calculated in euros and cents.

Markcheese

How many heating systems are you going to need for a house that doesnt really need heating ?? ( if its near passive)
My 200 year old crappy terrace cottage (with a modern crappy extension) is mainly heated with a small stove (no back boiler) we do have oil as a back up .. mostly I think our place is heated by the oven, tumble dryer, dishwasher ect ..

If you're worried you could pipe for rads and a boiler but not install them till you know you need them .pipe is cheap..

blast06

MicktheMan wrote: »

While, with your level of heating costs, it may not be economical to go TG, what is often overlooked is the thermal comfort upgrade that good TG windows give over DG windows. This comfort dividend cannot be calculated in euros and cents.

I'm not so sure .... if i go to my kitchen at 3am on a really cold night, then its still 20 degrees (have no thermostats ... just have heat curve constant at 30) with a 'fresh air' feel from MHRV. I don't see that i am missing anything to be honest. In fact, when i describe the entire insulation, heating, ventilation, air-tightness package to people and then say what my average heating bill is, i quickly add that the low heating cost is only part of the benefit - the other being the comfort factor.

MicktheMan

blast06 wrote: »

I'm not so sure .... if i go to my kitchen at 3am on a really cold night, then its still 20 degrees (have no thermostats ... just have heat curve constant at 30) with a 'fresh air' feel from MHRV. I don't see that i am missing anything to be honest. In fact, when i describe the entire insulation, heating, ventilation, air-tightness package to people and then say what my average heating bill is, i quickly add that the low heating cost is only part of the benefit - the other being the comfort factor.

You may have misinterpreted my comment as obviously you have excellent airtightness, insulation, etc. My comment was to do with one of the finer points about the difference between double and triple glazed windows.
I was referring to the radiant heat transfer effect that your dg glass has on your skin (but not on the thermostat) and therefore comfort, which is solved by good TG units.

blast06

MicktheMan wrote: »

You may have misinterpreted my comment as obviously you have excellent airtightness, insulation, etc. My comment was to do with one of the finer points about the difference between double and triple glazed windows.
I was referring to the radiant heat transfer effect that your dg glass has on your skin (but not on the thermostat) and therefore comfort, which is solved by good TG units.

OK, fair point.
I must be getting old cos i love nothing more than sitting down on the couch mid-morning on a Saturday after a long cycle, shower and late breakfast and snoozing on the couch with the mid morning sun splashing in the windows and warming me (i presume TG stops the 'warming'!) ..... although all those circumstances lining up is only about twice a year!!

BryanF

blast06 wrote: »

(i presume TG stops the 'warming'!) ..... although all those circumstances lining up is only about twice a year!!

Exactly!

Twice a year verse a window that actually makes a difference to heat loss

May I repeat, it's about Heat loss as a balance with heat gain.

A 3G window might let 50% light/heat through, where as a 2g might let 60% through

Balance that with 18? Hours where loss outweighs gain and your double glazing is probably a negative value over the heated season.

As pointed out above this is also about comfort. Add comfort & reduced heat loss, and the unnoticeable light/heat loss, 3G will win every where bar maybe in some south west coast areas where it's more about wind than cold temps

If you go back through the years of boards, many great arch techs have explained this is greater detail and with more figures.

the best double glazing at ~1.2wm2k is equal to about 20mm insulation where as 3G ~0.8wm2k equal to about 40mm insulation.

1.2w/m2k will keep the internal Surface temp above ~12degs (very approx condensation point in Irish homes) for much of the year but 3G will
Stop you loosing much of the gained heat

Thermal mass is great but the solar gain of double doesn't balance with the heat losses

blast06

BryanF wrote: »

Exactly!

Twice a year verse a window that actually makes a difference to heat loss

May I repeat, it's about Heat loss as a balance with heat gain.

A 3G window might let 50% light/heat through, where as a 2g might let 60% through

Balance that with 18? Hours where loss outweighs gain and your double glazing is probably a negative value over the heated season.

As pointed out above this is also about comfort. Add comfort & reduced heat loss, and the unnoticeable light/heat loss, 3G will win every where bar maybe in some south west coast areas where it's more about wind than cold temps

If you go back through the years of boards, many great arch techs have explained this is greater detail and with more figures.

the best double glazing at ~1.2wm2k is equal to about 20mm insulation where as 3G ~0.8wm2k equal to about 40mm insulation.

1.2w/m2k will keep the internal Surface temp above ~12degs (very approx condensation point in Irish homes) for much of the year but 3G will
Stop you loosing much of the gained heat

Thermal mass is great but the solar gain of double doesn't balance with the heat losses

Just as well i didn't read threads like this when i was building or i would have got completely bogged down on what to do!!!
Still though (ridiculously hypothetical scenario coming up!!) if i had no mortgage and won a hundred K and a windows supplier said i can convert all your existing windows to 3G for 3 grand ..... then i wouldn't bother, i.e.: i can't see that it would pay for the investment given my heating bills and to be honest, i still have to pinch myself every so often when i think about the comfort factor i already have.

Anyway, discussion is about where OP could cut back on costs so just offering my experience.