New Build - heating and insulation question

juniorballyc

Hello, starting build early next yr - a 2,200sq ft 2 story house.
We're trying to figure out what spec for insulation we should go for before we go for tender. We really want to get this right to minimise heating costs down the line. Unfortunately like most we are on a tight budget.

Firstly, let me point out that we are pretty clueless on this subject. We have planning for solar panels but we are not sure now whether to include them or not after talking to different friends and builders - basically they are saying they haven't been proved yet re lifetime and if they really do pay for themselves.
After trawling through searches online, the common thing that comes up is getting your insulating right and that is more important than heating system.

So I suppose my question to you is...what type of insulation is best in the walls, how much of it and same for attic?

With regarding heating system, we are now thinking solid fuel stove with back boiler and perhaps heating rads? Are there any other ways to use a stove to heat house? We heard of a house that had 2 pipes coming from stove pumping heat directly into 2 other rooms - is this a done thing?

Any advice would be great plz

sinnerboy

See here

juniorballyc

Thanks sinnerboy - great post

Idbatterim

does the house have access to natural gas line or what fuel do you plan on using?

juniorballyc

Idbatterim wrote: »

does the house have access to natural gas line or what fuel do you plan on using?

Sorry, forgot to say - oil

beyondpassive

For new house house heating systems we are seeing the following solutions (all with treble glazing, 250mm of insulation, MHRV and cold bridge free details).

1. 6m2 of solar tubes, 750L accumulator with underfloor and towel rads, LPG or grid gas boiler

2. Air source heat pump (N..e, D....s or O...r) linked to preheat tank and cylinder with 2kW PV array. Underfloor

3. 14kW back boiler stove (room sealed) 4kW to room, fueled by seasoned timber, linked to 600L accumulator tank and with either heater batteries or ducted air to be distributed by the MHRV system. with 2 towel rails. Note this system does not comply with part L renewables obligation and requires a dispensation from county building control. Would likely need to be a passivhaus to get the dispensation. With this sub-optimum system it would be advisable to plumb the infrastructure for adding renewables in future. i.e PV brackets and pop up for future heat pump.

sinnerboy

beyondpassive wrote: »

1. 6m2 of solar tubes, 750L accumulator with underfloor and towel rads, LPG or grid gas boiler

Solar contributing to SHD and needing to do "extra" calculation sheet for DEAP?

beyondpassive

sinnerboy wrote: »

Solar contributing to SHD and needing to do "extra" calculation sheet for DEAP?

Appendix Q Solar Space Htg - “AppQ_SolarSpaceHtg_April_09.xls” Excel workbook www.seai.ie/.../DEAP/AppQ_SolarSpaceHtg_April_09_xls.xls

DEAP Procedure for Active Solar Thermal Systems contributing to both Domestic Hot Water and Space Heating Requirements (Individual Heating Systems)
www.seai.ie/.../DEAP/AppQ_SolarSpaceHtg_April_09.pd

hge19

Insulation will be a standard detail. I wouldn't be too concerned about renewables...A good design that has airtightness at it's core and utilises a heat exchanger would be what I'd look in to. Only a though!

ShiverinEskimo

beyondpassive wrote: »

2. Air source heat pump (N..e, D....s or O...r) linked to preheat tank and cylinder with 2kW PV array. Underfloor

I think it's ok to name manufacturers on here - just not actual suppliers/installers. (Apologies to the mods if my going by that link is no longer applicable - searching for heat pump suppliers gets that thread as the top google result)

I got Nibe, but I can't figure out the other two.

The Parrot

well what my plan is to run a 18kw solid wood gasifying burner into a 1000lt buffer tank in a highly insulated house. with under floor heating. from what i can see this will do the job nicely.
my plan is to have a solar coil in the tank as well for future proofing and running solar into a 300lt hot water tank as i dont think i can afford the money for the panels to heat 1000lt and cant afford the tank with a dhw element yet.

should point out i am looking to heat a 3400 ft house with 300mm in the floors on a well detailed strip foundation.
and timber frame with a wall u value around the 0.12/.14

fclauson

hge19 wrote: »

Insulation will be a standard detail. I wouldn't be too concerned about renewables...A good design that has airtightness at it's core and utilises a heat exchanger would be what I'd look in to. Only a though!

NO NO NO

read my artical in CI - there is a MASSIVE issue with Passive houses and Part L compliance - to reach DEAP defacto compliance for renewables you have to "strap on" eco bling - or make pragmatic choices

think of it like this - my total heat demand is 13.5Kw/m2/Annum - and the regs insisit I use renewables to get 10Kw/M2/Annum (or 4kw/m2/annum electrical)

So even with solar thermal (a non efficient return on investment) and a HP (no they are not as expensive as some think) and a wood only stove I would be way off my requirment for PART L

What did I do - I put 16 SQm of PV - why - from a Return on investment perspective it has the best pay back (probably about 12 to 16 years)

With this I will get A1 to keep the DEAP team happy and Passive Certified (the only one with the combo in the country I think)

Do not beleive sales folks who say "a xxx will meet you Part L" - 'cause it won't !!!!!

Do the maths and make sure - I was speaking to someone with a finished house - which is well insulated, cheap to run etc etc - but NOT PART L COMPLIENT and which is causing him a headache (say no more)

sas

fclauson wrote: »

What did I do - I put 16 SQm of PV - why - from a Return on investment perspective it has the best pay back (probably about 12 to 16 years)

You've been very open to sharing your figures in the past. Any chance we can see these?

lowkeys

For how much insulation is required i would contact the insulation suppliers and give them a copy of your plans. They will then make recommendations as to what is required to meet the building regs. If you give them to the 3 main suppliers you can then compare prices against u-values.

fclauson

sas wrote: »

You've been very open to sharing your figures in the past. Any chance we can see these?

will do at week end (if I remember - ping me if I forget)

beyondpassive

lowkeys wrote: »

For how much insulation is required i would contact the insulation suppliers and give them a copy of your plans. They will then make recommendations as to what is required to meet the building regs. If you give them to the 3 main suppliers you can then compare prices against u-values.

I don't see that they can do this. How does this work, in order to specify insulation wouldn't the suppliers need to do a full DEAP BER assessment and know:
1. the standard of windows
2. types of heating (including renewables) and ventilation system and
3. the airtightness and thermal bridge strategy.

The construction industry is just now waking up to how radically the changes to building practice, brought on by Part L 2011 are. Self builders and building certifyers should ignore the new regs at their peril. Building control are getting their act together. I've heard that wexford are now doing 4 site visits to the majority of one-off houses going to site since last month.

sheff the ref

I cant figure out why someone would even think about taking a shortcut on insulation.

Insulation is
(a) Not terribly expensive compared to some aesthetic household items e.g. porcelain tiles, hand painted kitchens etc. etc.
(b) Possibly the best investment in any house as it prevents heat loss which lowers heating costs.
(c) It provides less long term financial stress and you don't have to worry about where the next €1000 for a tank of oil will come from

Anyhow my house is at the design stage at the moment. Probably will end up a compact 1600-1700 square feet with a converted attic that may never be a living area. It will be a block wall house and downstairs there will be Kitchen, Utility/Plant Room, 2 Sitting Rooms, 4 Bedrooms (2 compact ensuite, 1 walk in wardrobe), 1 Bathroom, Sunroom.

At the moment I am looking at borehole Geothermal Heating System with underfloor heating. I will have at least one stove with a back boiler probably in the Sitting Room off the Kitchen. I would also be having solar. Regardless of heating sources, I am operating on the philosophy that an insulated house retains the heat, so I am very conscious of heat retention. I am very wishy washy about a HRV system. Some people reckon that in the long run they cost more than they save between maintenance and running costs.

I am looking at the following insulation:

Windows:
South and West Facing Walls - Double Glazed Windows to facilitate passive gain
East Facing Back Wall - Triple Glazed Windows
North Facing Gable - Either Triple Glazed Windows or perhaps No Windows

Insulation:
150mm Cavity pumped with beads
50mm Internal Insulated Plaster Boards

And obviously the relevant attic insulation.

Any suggestions or ideas or recommendations???

sas

sheff the ref wrote: »

I cant figure out why someone would even think about taking a shortcut on insulation.

I am looking at the following insulation:

Windows:
South and West Facing Walls - Double Glazed Windows to facilitate passive gain
East Facing Back Wall - Triple Glazed Windows
North Facing Gable - Either Triple Glazed Windows or perhaps No Windows

I have most of my glazing on the south and it's all triple glazing. My living area was 24 degress when we got home yesterday. There is a difference between double and triple glazing as regards solar radiation being allowed in. However, there is also a difference with the amount of heat they let out. The passive solar gain isn't a huge contributor for vast amounts of time during the winter, choosing double glazing for the south however punishes you 24/7 for the winter. Remember, we typically have more dark damp dreary days than cold bright days. I'd be happy for it to be blue skies and 0 degress all winter, I'd have no need for heating at all and tank fulls of hot water.

I do however also have HRV which you have issues with so I'm not sure we'd really see eye to eye anyway.

sheff the ref

The issues I have with HRV involve stuff like Kitchen Vapours, Oil etc clogging up the system. I remain unconvinced that the system pays for itself but am there to be won. It basically swops stale air for fresh air without heat loss. However I reckon that there is ample opportunity for fresh air to enter the house when doors are opened and closed. Bathroom windows will be open for a certain length of time as well regardless of HRV.

If the sun through triple glazing in this freezing cold allowed 24 degrees heat into your living areas then the perception that it is a barrier to passive gain is only a myth. On that note, it must be an exceptionally good winter for solar, we are having a lot of sun every day this winter.

How is your house insulated???

beyondpassive

beyondpassive wrote: »

Building control are getting their act together. I've heard that wexford are now doing 4 site visits to the majority of one-off houses going to site since last month.

Who is it that does these inspections ? Its a pity they were not done during the boom. Why does every part of the construction not have to be signed off by the Council ?

It Might prevent some rogue builders removing the steel from foundations before they are set:eek:

sas

Deleted User wrote: »

Why does every part of the construction not have to be signed off by the Council ?

That would make them responsible for what they signed off on and open to being sued if something actually goes wrong.

Down with that sort of thing etc.

sheff the ref

sheff the ref wrote: »

Insulation:
150mm Cavity pumped with beads
50mm Internal Insulated Plaster Boards

Hi Sheff at similar stage to yourself: Does the installation of internal insulated plaster boards like this not cause a risk of condensation on the joint between the external wall and one of the internal wall(room side of the insulation) as this section would be colder than the insulated wall ?

Would it not be better to increase the size of the cavity insulation and leave the internal wall not insulated ?

sas

sas wrote: »

That would make them responsible for what they signed off on and open to being sued if something actually goes wrong.

Down with that sort of thing etc.

It would justify the stamp duty and council contributions and upcoming property tax. Of course in this county brown envelopes would be used to turn a blind eye.

Where i live an estate has been designated as been in a flood zone by the same council that allowed the estate to be built 7 years ago. Now no houses can get insurance and they are unsaleable. Time for councils to take responsibility.:( End of rant

sinnerboy

Deleted User wrote: »

Time for councils to take responsibility.:(

Moderator note
All agreed on that - but please back on topic now

Idbatterim

oil will be cheaper than lpg, you could get wood burning boiler like below. Some of them only require feeding every week or two, see below link.

http://www.madaboutheat.com/

personally I really question the cost, complexity, repay period of all these "fancy systems" If people are really concerned about energy costs, why heat up hundreds of litres of water every day, when most if not all of it might not even be used. Why not just have it instant, unlimited at the source? The only thing I use hot water for is out of shower or bath (dishwasher and washing machine heat their own water). Why not just have Zone the heating systems for living areas and bedrooms. Nobody can argue with the insulation, If money tight, I would at least opt for triple glazing in the bedrooms.

http://www.ebay.co.uk/itm/Bargain-for-Dafi-Instant-Water-Heater-Tankless-Compact-2-years-warranty-/280833909613?pt=UK_DIY_Materials_Plumbing_MJ&var=580074129600&hash=item416301636d

from what I saw the other day, ones in bathroom can be hooked up to provide for hot water tap and shower / bath together.

I know you dont need direct sunlight for solar panels, but the fact is, when you need them most, the sun and UV is at its least i.e. in winter!

sas

Idbatterim wrote: »

I know you dont need direct sunlight for solar panels, but the fact is, when you need them most, the sun and UV is at its least i.e. in winter!

Solar panels are in the vast majority of cases used to produce domestic hot water. They simply aren't used for heating.

I'm not aware of any evidence to suggest we all take cold showers for 7-8 months of the year.

So your statement is completely wrong.

Idbatterim

Solar panels are in the vast majority of cases used to produce domestic hot water. They simply aren't used for heating.

I'm not aware of any evidence to suggest we all take cold showers for 7-8 months of the year.

So your statement is completely wrong.

no we dont take cold showers for 7-8 months of the year, but you always need a back up system with solar, if its only heated to 25-30degrees, i take it you get the normal hot water tank or boiler to bring it up to the desired heat?

sas

Idbatterim wrote: »

no we dont take cold showers for 7-8 months of the year, but you always need a back up system with solar, if its only heated to 25-30degrees, i take it you get the normal hot water tank or boiler to bring it up to the desired heat?

My tank is 50 degrees today purely based on solar.

I've no idea what a normal hot water tank that somehow heats water is.

For 7-8 months of the year you need absolutely nothing else. My tank, all 1000 litres of it was 70 degrees in July.

You've a very poor level of understanding of what you refer to as "fancy systems " it would appear.

Idbatterim

well what my plan is to run a 18kw solid wood gasifying burner into a 1000lt buffer tank in a highly insulated house. with under floor heating. from what i can see this will do the job nicely.
my plan is to have a solar coil in the tank as well for future proofing and running solar into a 300lt hot water tank as i dont think i can afford the money for the panels to heat 1000lt and cant afford the tank with a dhw element yet.

its relative. the likes of the above sounds pretty complex to me as opposed to this, which i have in my family home in dublin (no need for pump as pressure more than adequate). no hot water tank, no tank in the attic, no pumps, no panels, just a gas boiler, that heats up unlimited water for dhw and rads on demand. Now Id like to know, given the simplicity of such a system, how much do you not only save on the upfront cost, what about the maintenance cost and the extra space you have? Im playing devials advocate here, there are a lot of factors to take into account. I dont have an agenda...

sheff the ref

What size cavity would you propose to compensate???

Deleted User wrote: »

Hi Sheff at similar stage to yourself: Does the installation of internal insulated plaster boards like this not cause a risk of condensation on the joint between the external wall and one of the internal wall(room side of the insulation) as this section would be colder than the insulated wall ?

Would it not be better to increase the size of the cavity insulation and leave the internal wall not insulated ?

ShiverinEskimo

I'm mid-way through the build and unfortunately a wide cavity was still a bit off being 'standard' enough to be a possibility way back at the design and planning permission stage.

If I was designing again I'd go with e 250mm pumped cavity and forget about insulated plasterboard. Shouldn't be too expensive these days to do so and leaves with a great thermal mass and no fúcking around if you want to screw something to the wall inside.

MicktheMan

sheff the ref wrote: »

The issues I have with HRV involve stuff like Kitchen Vapours, Oil etc clogging up the system. I remain unconvinced that the system pays for itself but am there to be won. It basically swops stale air for fresh air without heat loss. However I reckon that there is ample opportunity for fresh air to enter the house when doors are opened and closed. Bathroom windows will be open for a certain length of time as well regardless of HRV.

Have you ever visited a house with mvhr installed and spoken to the owners about its benefits? If not then perhaps you should.
Your statement above "basically swops stale air for fresh air" misses the point. A ventilation system's function is to replace the internal "wet" air with external "dry" air in a controlled manner. It's all about internal moisture control. Get this wrong in the context of modern builds/lifestyles and you run a very real risk of mould.

just do it

beyondpassive wrote: »

I've heard that wexford are now doing 4 site visits to the majority of one-off houses going to site since last month.

I for one am delighted to hear that, pity it is now 15yrs too late.

sheff the ref

Would you get the same heat retention with a wide 250mm cavity, as you would by having the walls lined internally with insulated plasterboard.

Are there any further things to be taken into account where there is a wider cavity, I presume a wider cavity means that a wider foundation is needed?

ShiverinEskimo wrote: »

I'm mid-way through the build and unfortunately a wide cavity was still a bit off being 'standard' enough to be a possibility way back at the design and planning permission stage.

If I was designing again I'd go with e 250mm pumped cavity and forget about insulated plasterboard. Shouldn't be too expensive these days to do so and leaves with a great thermal mass and no fúcking around if you want to screw something to the wall inside.

sheff the ref

Ya havent seen it but spoken to a few people on the phone. Another problem seems to be that people will invariably open windows in a house 'to let in fresh air' which more or less renders the system redundant.

MicktheMan wrote: »

Have you ever visited a house with mvhr installed and spoken to the owners about its benefits? If not then perhaps you should.
Your statement above "basically swops stale air for fresh air" misses the point. A ventilation system's function is to replace the internal "wet" air with external "dry" air in a controlled manner. It's all about internal moisture control. Get this wrong in the context of modern builds/lifestyles and you run a very real risk of mould.

ShiverinEskimo

Wall ties get expensive when you move into those widths but they are coming down all the time - two years ago when I started designing they were prohibitively expensive but not anymore. If you detail it correctly and go air-tight you should have a very good result from the cavity alone.

The inner leaf will offer a good heat-store/thermal-mass too if you go with under-floor heating which you don't get with drylining. And as I said above, you'll be laughing when it comes to mounting TVs, wall-lamps, curtain rails, pictures etc.

john_cappa

How much are the wall ties for 250 or 300 mm cavities ?

ShiverinEskimo

No idea.

You'd have to ask my architect.

sheff the ref

sheff the ref wrote: »

What size cavity would you propose to compensate???

It was more of a question than a statement!

sas

sheff the ref wrote: »

The issues I have with HRV involve stuff like Kitchen Vapours, Oil etc clogging up the system. I remain unconvinced that the system pays for itself but am there to be won. It basically swops stale air for fresh air without heat loss. However I reckon that there is ample opportunity for fresh air to enter the house when doors are opened and closed. Bathroom windows will be open for a certain length of time as well regardless of HRV.

Ok, my kitchen extractor is the recycling type. The nearest HRV extract is approx 15 feet away and is protected by a special filter. This should minimize the risk of grease etc. affecting HRV.

As for payback, my thoughts are this. It somewhat comes down to how hot you like your home. Say (like me) you would like 23 - 24 for the room where you sit at night. If you have that heat being vented to outside, it will cost quite a bit to get it back. My HRV is a large unit because I've a large house. Electricity usage on it is at 10euro per month, I measured it a few months back. There is then the cost of filtsers which could bring my yearly spend up to €300. That's not a small amount. My house is close to 4000sq foot though so those costings need to be considered in the scale of our home. A smaller unit will be cheaper to buy and cheaper to run.

A friend of mine moved into a PH 2 years ago. He'd run short of money and couldn't commission the HRV so he resorted to opening windows to ventilate etc. He was disappointed with the performance of the house. This all changed when the HRV was installed. The temperature in the house is pretty constant. You must also take this into account.

Bathroom windows are never opened in my house. The bathroom HRV extract is over the shower and it deals with the steam. This time of year with lower temps, I do get a very light condensation on the window and the top of the mirror in the bathroom after someone showers. It takes 10mins for this to fully clear.

With HRV it is a choice to open windows, it is never going to be a requirement if the system is installed correctly.

Personal preference plays its part. Someone here did comment that their wife insists on openings windows because she only associates fresh air with cold air.

sheff the ref wrote: »

If the sun through triple glazing in this freezing cold allowed 24 degrees heat into your living areas then the perception that it is a barrier to passive gain is only a myth. On that note, it must be an exceptionally good winter for solar, we are having a lot of sun every day this winter.
How is your house insulated???

As I depend upon the sun for my heat, I'm pretty sensitive to the amount of sunshine we get in winter and I wouldn't degree that it's been any better than any other winter. I'm on Laois so it depends where you live. The last 2 days have been very good, nice and warm in main living area and there was sufficient solar to allow us to run the UFH directly off the tank ( solar heated water) for those rooms that don't get solar gain.

My house is built with the aim of being certified passive. It has a foot of external insulation on it and we also achieved one of the best airtightness results in the country (I'm very proud of this so you're going to have to accept a small amount of grand standing on it).

beyondpassive

Insulation should be in the one zone, dry lining is ineffective and a pain to fix to. Wide cavity is fast becoming the standard build, but it needs to be build in accordance with detailed technical assembly drawings from a technologist.

Wide cavity wall ties
250 cavity blown bead = 400mm long stainless steel tie =80c ea
300 cavity blown bead =450mm long stainless steel tie =90c ea
Single partstainless steel wall tie with 17x2.5mm cross sectional area
installed 5 per meter square and 10 per meter at openings and eaves closer. (or as approved by your structural eng to suit site conditions.

The wall ties reduce the effective conductivity of the cavity bead by 25%. So if your bead is platinum 0.033WmK is reduced to 0.041W/m-K

From this we get a wall U-Value of 0.154 W(m2/K) when we average out the wall tie spacing.

Rushy Fields

Can anyone tell/guide me? I have a 150mm cavity and it will be pumped with bead. I am "considering" putting insulated plasterboard on the inside of the external walls but what i am seeing here it seems to be better to not to put up the insulated slabs and just to use the block as a thermal store. I was thinking rather than let the block retain the heat that the insulated board would stop the heat going out and keep it the heat in the room. Any advice is welcome.....

beyondpassive

nealger wrote: »

Can anyone tell/guide me? I have a 150mm cavity and it will be pumped with bead. I am "considering" putting insulated plasterboard on the inside of the external walls but what i am seeing here it seems to be better to not to put up the insulated slabs and just to use the block as a thermal store. I was thinking rather than let the block retain the heat that the insulated board would stop the heat going out and keep it the heat in the room. Any advice is welcome.....

Is the 150mm cavity fully build? if so you'll have to stick with your original strategy or revisit your DEAP compliance calcs.

The rational for not using drylining is that the block will act as a damper to intermittent heating, and will stabilise fluctuations in temperature and solar gain overheating. In other words, if your heating comes on twice a day in winter, the temperature will rise to 22 degrees and fall back to 17, so you have the goldilocks problem. Too hot when the heat goes on, too cold when not on. Having a block internal surface gives you over 25mm of mass which will act like a storage heater and absorb the room overheat and slowly release it.

The real reason we use wide cavity is for ease of fixings, improving thermal bridges and eliminating the fire risk of composite boards and wiring.

ivorfa

Surely your internal walls if built with block will be enough of a thermal mass even if your external walls is done with insulated plasternoard, I have yet to place my hand on a block built wall that was not cold unless above a radiator so surely a lot of heat is absorbed by these walls i am sure you would not get as much heat back from the walls as it takes to heat them. As the other poster said I would prefer to keep the heat in as opposed to heating the walls.If your house is properly insulated and airtight you should have no bother keeping the heat in a room and avoid excessive cycling on your heat source

sydthebeat

ivorfa wrote: »

Surely your internal walls if built with block will be enough of a thermal mass even if your external walls is done with insulated plasternoard, I have yet to place my hand on a block built wall that was not cold unless above a radiator so surely a lot of heat is absorbed by these walls i am sure you would not get as much heat back from the walls as it takes to heat them. As the other poster said I would prefer to keep the heat in as opposed to heating the walls.If your house is properly insulated and airtight you should have no bother keeping the heat in a room and avoid excessive cycling on your heat source

really? how sure?

the way i see the argument for insulated plasterboard is wholly about usage of the building.

yes, insulated plasterboard means a room warms up quicker, but it also means a room cools down quicker too. BP has outlined this phenomenon already.
So if you have a room that is only being used intermittently internal insulation does have its benefits.
For example the office i work in has pumped 110 cavity walls. Block inner walls.
The heating is set for regular intervals in the 9 - 5:30 working day.
The heating doesnt come on at weekends.
The office is always cold on monday / tuesdays as the building has to warm up ... by fridays its nice and toasty.
the heating times are not changed so whats the difference?
the difference is the thermal mass of the walls have to take in more heat after a significant "cooling off" period.

If you are going to use your house sparingly, with no one in it during the day, then perhaps insulated plasterboard is a suitable suggestion.
However if there is going to be someone in the home most a days, every day, then you do not want "heating up / cooling down" periods... you want to maintain a constant temp throughout, and the best way to do this is by utilising your thermal mass as a heat storage.

sheff the ref

A house with underfloor and geothermal will have a relatively constant temperature and would get away with internal block walls. A house with oil and rads would be more suited to insulated plasterboards.

sydthebeat wrote: »

really? how sure?

the way i see the argument for insulated plasterboard is wholly about usage of the building.

yes, insulated plasterboard means a room warms up quicker, but it also means a room cools down quicker too. BP has outlined this phenomenon already.
So if you have a room that is only being used intermittently internal insulation does have its benefits.
For example the office i work in has pumped 110 cavity walls. Block inner walls.
The heating is set for regular intervals in the 9 - 5:30 working day.
The heating doesnt come on at weekends.
The office is always cold on monday / tuesdays as the building has to warm up ... by fridays its nice and toasty.
the heating times are not changed so whats the difference?
the difference is the thermal mass of the walls have to take in more heat after a significant "cooling off" period.

If you are going to use your house sparingly, with no one in it during the day, then perhaps insulated plasterboard is a suitable suggestion.
However if there is going to be someone in the home most a days, every day, then you do not want "heating up / cooling down" periods... you want to maintain a constant temp throughout, and the best way to do this is by utilising your thermal mass as a heat storage.

Rushy Fields

Ok, just to add another bit to the decision making process. I have decided to put in heat MHRV, UFH using Geothermal. Will i not be able to keep the house at an ambient temp avoiding this heating up/cooling down process with all these other processes/systems even if i do decide to use the insulated board on my inside of the external walls.
The house will be mainly occupied during the evenings and obviously at night as both my OH and i work during the day from 7.30 to 6pm.
I have a lot of glass on the south facing and south west to capture solar gain. Seems like i will need alot of controls in place to avoid this heating up and cooling down? AND at what cost?

sheff the ref

The stats will dictate the consistency of the temperature, but you will be unable to control the temperature of the heat gained from the sun. Someone mentioned earlier in the week that they had 24 degrees heat one evening this week from the sun alone.

sydthebeat

sheff the ref wrote: »

A house with underfloor and geothermal will have a relatively constant temperature and would get away with internal block walls. A house with oil and rads would be more suited to insulated plasterboards.

partially true, the heat source and emitter type are only two parts of the complex system you need to ensure constant temperatures.

other parts include:
adequate heating controls
high insulation levels
minimised thermal bridges
minimised heat losses through air tightness


whether of not you'd "get away with" internal walls only is purely speculative. Passive houses can range from low thermal mass timber frame houses to high thermal mass concrete builds.

sinnerboy

High thermal mass will be vital to anybody who is relying on heat pump technology to help the comply with Part L renewables. Heat pumps only work economically when allowed to cruise - ask them to sprint and you will pay for that with high elec bills.

So high thermal mass buildings will tend to smooth over raising and falling external temperatures - the heat pump can be set to a gentle constant pace with the fabric being the buffer.

Low thermal mass buildings will heat up quickly but slow down quickly too. A heat pump in this scenario will be expensive to run especially during cold snaps.

beyondpassive

The idea of using exposed hardwall plaster/block on the inside has two additional benefits.

1. If the surfaces can hold 18 degrees this alters your perception of comfort as the walls dont take heat from your exposed skin. Stand near a block wall in an older house and you will feel your cheek get cold. ( I need to clarify, the cheek on your face). So when you have warm surfaces, an internal temp of 19 degrees feels like 21. your energy bills rise 7% for every additional degree you set the thermostat. So insulated mass, can reduce fuel use by about 14%

2. effectiveness of renewables.
In order to meet Part L 2011, we know that MHRV and treble glazed are the norm. But then to meet the renewables obligation of 10kWh/m2 in a house that used only 35 to 45 kWh for space heat and hot water, you have to use your renewables for space heat. This applies to solar panels or Heat pump. You need to design your fabric so that the house can be heated to comfort levels with a low grade heating delivery system. So underfloor and some from of accumulator tank is needed. An accumulator is a combined buffer/preheat tank and cylinder stacked together and highly insulated so that temperatures are stratified with 55 degrees on top, 40 in the middle and about 20 degrees minimum at the bottom. It allows you to use the the bottom portion to heat the underfloor. So on sunny days in winter, the 40 degrees coming off solar will heat the house. Equally the heat pump only has to lift water to 36 degrees. If the return water is coming back at 25 degrees or higher, it can utilise the heat stored in the buffer portion of the accumulator tank. If the tank hasn't got 36 degrees then the boiler fires or the heat pump ramps up. In order that the system water returning to the tank from the underfloor is kept close to the temp of the buffer, we insulate anything in contact with the underfloor to the highest degree possible. This turns the screed slabs into a big storage heater, insulate the walls externally and the walls become part of the storage heater.

A bit long winded, but thats why we say that underfloor is now the norm also.. By using low grade heat renewables or the occasional use of a boiler stove to heat the house when you have some heat banked, you reduce your running costs significantly. Your not doing this for Part L or Passivhaus reasons, you're doing it for comfort and running cost reasons.