Heating System for new build

funkey_monkey

Hi,

We're just about to start our new build and are finalising the heating system. We are opting for OFHC and two oil burners (one with a back boiler).

We are designing in the ability to retrofit a greener (probably PV) system at a later date if the systems improve.

The main kitchen will be heated by UFH (due to lack of wall space because of cupboards etc). The remainder of the house shall be heated via conventional radiators located under the windows. Walls will have a 6" pumped cavity and triple glazing. A similar standard of insulation will be installed in roofspace.

The question now relates to how to control the heating.

My idea is to have a zonal system where the bedrooms and probably the bathroom are in a zone. Another zone for the both living rooms and then the kitchen, toilet, and utility room separate.

My thinking for this is that it seems convention to group the bedrooms and bathroom - which seems fair enough as you usually only want to take the chill out of these rooms.
The kitchen temp will vary with cooking activity so it should be separate. Both living rooms together - even though only one room will be mostly used, it gives the ability to walk straight into the other room without need for temp ramp up.

Does this sound fair enough?

When it comes to monitoring the temperature in these rooms what is the best way? Builder was talking about using thermostats on the rads but I'm not sure how good a system that would be. I know someone who updated their house recently and fitted thermometers fitted to the ceiling which were fed into a control unit that opened and closed solenoids depending on the temperature. Any thoughts?

We are not planning on putting in a heat recovery system. Are we making a mistake here? The attic is being laid out for additional rooms when the time arises - do these things take up much space?


Thanks in advance for any replies!

893bet

Mvhr is not really optional if you want to meet building regs.

funkey_monkey

im up north so our regs are different.

BryanF

Ufh & rads: heated with oil? Your right, control will be a problem.
What's the air-tightness & ventilation strategy

funkey_monkey

BryanF wrote: »

Ufh & rads: heated with oil? Your right, control will be a problem.
What's the air-tightness & ventilation strategy

No real strategy that I'm aware of in regards to air tightness and ventilation. At least the architect has not mentioned anything to me about it as noteworthy. I'm assuming now that there will be vents in the soffits...

Why do you think that the ufh and rads controlled by oil will be problematic - is this due to the amount of insulation we are installing?

Calahonda52

typical UFH runs at a much lower temp than that for normal sized rads so you will have an added layer of complexity to reduce the water from the OFCH boiler, which might be 70 or 80 down to maybe 35, depends on the design temps. using lower temp in rads will up the sizes to a point which will be unacceptable aesthetically.

IMO UFH for one room is sort of mad: I know some people don't like them but there are kick board fan assisted water heated rads you can get.

The attic conversion will be an issue for your airtightness strategy.
You should design all the services now with airtightness in mind.

Personally I would install MHVR now and have the airtightness to the desired spec: this will solve the kitchen problem and the two living rooms being heated, the utility room can be used for clothes drying.
Seems a pity not to given the rest of the spec

this may help
https://www.nsai.ie/S-R-54-2014-Code-of-Practice.aspx
Am puzzled by this
We are opting for OFHC and two oil burners (one with a back boiler).

3 separate units?

Whats story re hot water

funkey_monkey

Oil burner located outside for central heating and hot water.
Oil burner for main living room with back boiler feeding into CH and HW.
Oil burner for sitting room (no back boiler).

I'll speak to architect tomorrow about his strategy for ventilation. It seems to be overlooked as it is not in my QS quote.

Are you saying that installing a mix of UFH and rads is a bad idea or complex solution? Our window level is quite low so we don't have much room underneath for radiators. I just assumed from the drawings that a small rad was all that was required given the level of insulation.

The attic is being built with windows, services, and insulation in place. When/if needed all that will be necessar will be to add permanent staircase (joists will be built now with frame to accept this).

Are you saying that MHVR will remove the need for UFH in the kitchen and utility room?

Thanks for your replies guys - this is what I need to get back to my architect before start the build.

Calahonda52

funkey_monkey wrote: »

Oil burner located outside for central heating and hot water.
Oil burner for main living room with back boiler feeding into CH and HW.
Oil burner for sitting room (no back boiler).

Outside boiler in 2016 is just insane, IMhO

Having another oil burner with a back boiler linked up to the CH system with you spec is even more insane IMhO

What do you mean by oil burner in sitting room? Have u a link to the actual unit?

funkey_monkey wrote: »

I'll speak to architect tomorrow about his strategy for ventilation. It seems to be overlooked as it is not in my QS quote.

It may be just room wall vents and ventilated soffits.
Whats the exact roof design from slates in?
Slates.......... skimmed plasterboard

funkey_monkey wrote: »

Are you saying that installing a mix of UFH and rads is a bad idea or complex solution? Our window level is quite low so we don't have much room underneath for radiators. I just assumed from the drawings that a small rad was all that was required given the level of insulation.

No comment till u explain the need for 3 oil burners.

funkey_monkey wrote: »

The attic is being built with windows, services, and insulation in place. When/if needed all that will be necessar will be to add permanent staircase (joists will be built now with frame to accept this).

Then the A/T layer should get done properly now

funkey_monkey wrote: »

Are you saying that MHVR will remove the need for UFH in the kitchen and utility room?

Yes, you may need additional in line heaters for supplementing the basic heat recovery, depending on the loads in the house.

funkey_monkey wrote: »

Thanks for your replies guys - this is what I need to get back to my architect before start the build.

Glad to ask the hard questions!

On the A/T, you need to agree a figure and have this put in the contract, and agree interim tests during the build, however, your builder may baulk at the whole idea as it means more attention to detail for them, so they may try drive up price.
Have you a contract agreed with builder?

funkey_monkey

Calahonda52 wrote: »

Outside boiler in 2016 is just insane, IMhO

Having another oil burner with a back boiler linked up to the CH system with you spec is even more insane IMhO

What do you mean by oil burner in sitting room? Have u a link to the actual unit?

This is my fathers ideas. The reason for the oil burners is that the initial plan showed solid/log burners. He doesn't want hassle of purchasing bags of logs, carting them into house and cleaning the burner so is opting for oil in both rooms. They want a means of heating each room with its once heat source - instead of radiators only.
The idea of the back boiler was to get more use out of the main burner.
Outside burner is just intended for topping up.

The reason for this is that he doesn't want to install any ground pumps or water panels. Ground pump - insufficent ground for a proper system. Panels - not happy with the current performance vs payback tradeoff.

The units have not yet been specc'ed for the house. Going for final plans in a few weeks time. Hence me on here trying to resolve some things!

Should we be getting an engineer to do a heat survey first and then decide if these are needed? Honestly, I think my father wants to have chimneys in these rooms so that it is future proofed if there is a change of plan - and a burner will ensure that there is otherwise no (little) heat loss up the chimney as in the case of an open fire.

It may be just room wall vents and ventilated soffits.
Whats the exact roof design from slates in?
Slates.......... skimmed plasterboard

I'll dig this out tomorrow as I don't have it to hand.

No comment till u explain the need for 3 oil burners.

Any comment on this now and the plan for the 3 burners?

Then the A/T layer should get done properly now

A/T? Architect?

Yes, you may need additional in line heaters for supplementing the basic heat recovery, depending on the loads in the house.

Removing the UFH would be good.

On the A/T, you need to agree a figure and have this put in the contract, and agree interim tests during the build, however, your builder may baulk at the whole idea as it means more attention to detail for them, so they may try drive up price.
Have you a contract agreed with builder?

Nope, waiting on final plans to send out for quotes. We are in NI so this might affect some aspects of your replies as our regs are different.


Would a MHRV make the need for an external Oil burner redundant?

funkey_monkey

What levels of insulation are being used in the South?

Can you get an engineer to calculate the values? I might push for a report if so.

Calahonda52

A/T is airtightness layer which is the most critical aspect of the design from a heat retention point of view.

the A/T layer stops uncontrolled ventilation which is the key to heat loss.

MHVR and normal wood burning stoves/chimneys are a bit trickier, have no experience of oil burner stoves, are they 100% sealed and fan assisted?
Anyway, this combo is beyond my pay grade

Re
Would a MHRV make the need for an external Oil burner redundant?

properly done would make all three redundant.

If this house is for your folks then constant temp throughout the house would be the target in my view.

Re
We are in NI so this might affect some aspects of your replies as our regs are different.

Forget about regs, build to the best possible standard you can finance at this point as it will increase the comfort in the house a 1000 fold and with higher outlay up front, if done properly, will lead to much lower running costs.

Have you read up on the Passiv Haus standard and the associated energy foot print: u can use the standard as a design tool but not pay for certification.

Re this from me last night
On the Air tightness you need to agree a figure and have this put in the contract, and agree interim tests during the build, however, your builder may baulk at the whole idea as it means more attention to detail for them, so they may try drive up price.
Have you a contract agreed with builder?

Dont rush the tender docs out until you understand the issues here so tease them out here a bit more because once the docs go out, the pudshback will start.

funkey_monkey

The reason for the oil burner outside was to have the possibility of hot water without the need for heating any rooms at the same time.
All 3 running off oil was to minimise number of fuel sources required.
He wants chimneys in the house to have incase for future use. Hence having stoves in both rooms to seal the chimney.

TBH - I think he would be very wary of a house with no heat source other than a MHRV.

How do people obtain only hot water in these houses?

properly done would make all three redundant.

Properly done? How often are they 'properly done'? Are they difficult to spec or set up?


Can I ask what your job is?


I think he initially looked at passive houses but was put off by what the contractors were offering in terms of cost and lack of certificate.

sydthebeat

funkey_monkey wrote: »

The reason for the oil burner outside was to have the possibility of hot water without the need for heating any rooms at the same time.

this can be very simply achieved by control measures. Your oil boiler programmer should have a simply mechanism to select heating 'hot water and central heating' or 'hot water only'

sydthebeat

funkey_monkey wrote: »

TBH - I think he would be very wary of a house with no heat source other than a MHRV.
.

MHRV is not a heat source, unless you fit a heating element to it.

all it does is provided recovered heat to rooms, but that heat must be produced elsewhere.

One oil boiler is sufficient.

funkey_monkey

sydthebeat wrote: »

One oil boiler is sufficient.

There will be a single oil burner located outside.
Inside there will be two oil fired stoves, one in each living room. The one in the main room may also have a back boiler.

Are you suggesting to remove the back boiler from the stove in the main room? That would mean during winter that both stove and outside burner are in operation. He would not be getting maximum use out of the stove.

Your oil boiler programmer should have a simply mechanism to select heating 'hot water and central heating' or 'hot water only'

Yes, our current house has this arrangement.

They are old folk and like to have a fire in the room.

Calahonda52

sydthebeat wrote: »

MHRV is not a heat source, unless you fit a heating element to it.

all it does is provided recovered heat to rooms, but that heat must be produced elsewhere.

One oil boiler is sufficient.

Agree 100% that the normal situation is that there is a heat source external to the MHRV, however I saw one in Germany where it was in line water heated coils on the supplies that kept it all cosy: the heat source was gas but could be run on elec either which gives alternative primary energy sources without changing the kit.


The usual heat source is a wood burning stove, not a multi fuel as it is not "eco/green" enough, mind blank on correct terminology...:(

OP
He would not be getting maximum use out of the stove.
This makes little sense: what are the efficiency specs for the "central heating boiler versus the room oil stove

I think he initially looked at passive houses but was put off by what the contractors were offering in terms of cost and lack of certificate.
This is exactly what I was driving at earlier:
The conversations down here go along the lines of : Jaysus bud, why would you be bothered doing THAT?
I also said that it is possible to achieve the PH standard without actually paying for the formal cert which can be displayed in the house.
From memory, full blown PH requires max Air changes of 0.6 ACH ( air changes per hour) at 50 paschals pressure and max energy demand of 15kWhh per metre squared per annum.

Yes PH is not as cheap as builder finish with minimal attention to A?T and insulation.

However if you do the math comparing the difference in running costs over say 40 years for standard house versus PH and you factor in inflation, higher interest rates and energy costs maybe 10 times what they are now, the payback on the initial additional capital cost is there, no question.
The problem is most folk just don't want to see it, especially as in the long run we are all dead

funkey_monkey

I've hopefully talked him into getting an engineer to look over the plans and give their opinion of the heat 'strategy' for this house. I think he got spooked when I mentioned to him about the ventilation being overlooked.

Personally, I would have liked to have seen PV cells for heating water and the surplus being fed to the grid (if possible). Not keen on the water panels due to the fact that there is nothing than can be done with the surplus. I just think getting a raw input such as electricity gives more benefit/options.
However, from our initial look at them it would seem that by the time they are close to paying back, they are due for renewal. I'll get conduit put it place to handle the system but delay installing them until everyone is satisfied with there performance versus lifespan.

What are most people doing down south for heat sources in the house? I thought log burners were all the rage? Are people now just going with rads/UFH and no dedicated heat source in the main living areas?

funkey_monkey

Just checked - external walls to have U-Value of at least 0.21, roof of at least 0.18.

sydthebeat

funkey_monkey wrote: »

Just checked - external walls to have U-Value of at least 0.21, roof of at least 0.18.

Very unlikely to comply with building regs.

Edit
Oops your up north aren't you? If so please ignore. But still poor u value levels

funkey_monkey

What you looking for down south?

sydthebeat

funkey_monkey wrote: »

What you looking for down south?

my standard u value for wall is 0.14 and for roof is 0.11

mrsWhippy

sydthebeat wrote: »

my standard u value for wall is 0.14 and for roof is 0.11

Syd, how do you typically achieve these values?
Thanks

sydthebeat

mrsWhippy wrote: »

Syd, how do you typically achieve these values?
Thanks

150 xtratherm cavity fill insulation in walls

300 knauf earthwool rafter roll 0.036 on ceiling

funkey_monkey

I think our house will have similar. The walls are having a 150mm pumped cavity too. I think the roof will be to a similar standard. Maybe the ratings are purposefully pessimistic and are likely to be much better.

sydthebeat

funkey_monkey wrote: »

I think our house will have similar. The walls are having a 150mm pumped cavity too. I think the roof will be to a similar standard. Maybe the ratings are purposefully pessimistic and are likely to be much better.

My spec is not a 150 pumped cavity.

funkey_monkey

Sorry - I misread - it is marked as platinum ecobead. Why would you pump into a new build instead of using the boards - which is what I had assumed was being done.

BarneyMc

funkey_monkey wrote: »

Sorry - I misread - it is marked as platinum ecobead. Why would you pump into a new build instead of using the boards - which is what I had assumed was being done.

Not too many builders take care to fit the boards properly and that's putting it mildly.

funkey_monkey

The max board depth is 120mm - that leaves a 30mm air gap in the cavity. For a 150mm cavity do people max it out with a 100mm board back to back with a 50mm board or just go with 120mm board and an air gap?

How would a platinum ecobead perform against both these scenarios?

sydthebeat

funkey_monkey wrote: »

The max board depth is 120mm - that leaves a 30mm air gap in the cavity. For a 150mm cavity do people max it out with a 100mm board back to back with a 50mm board or just go with 120mm board and an air gap?

How would a platinum ecobead perform against both these scenarios?

There is a 150 full fill board option

funkey_monkey

Kingspan seem to be quoting 0.20 for a similar construction to my parents house if I have read this table correctly:
http://www.kingspanecobead.com/index.php/u-value

That just seems to be scraping past the less than 0.21 limit on the plan. I've searched for a u-value for the Xtratherm but could not see anything definitive for 100mm block (rendered) - 150mm cavity - 100mm block (plastered).

Would there be much of a difference in price between these two products and do I need to ensure that the windows(which will be triple glazed) are of a compatible u-value in order to avoid cold spots creating drafts?


Thanks - lots of good info to pass on here.