Photovoltic to run Geothermal Heat Pump

Quazzie

Hi,

I'm in the process of plans and pricing for the construction of my own first house. I've already decided on Geo-thermal heat pump linked to UFH as the way to go but am worried about some recent bad press they have recieved regards there allegadly fabricated eco credentials, due to the Electricity required to power them. So lately I've been toying with the idea of installing some Photovoltic solar panels with the sole use of powering the heat pump, therefore making it trully free and eco friendly. My problem is I am totally clueless regards anything electrical and would like some advice regarding (a) what size panels and Geo-thermal pump I'd need to heat a 3200sqft house (b) the initial cost of this system and (c) do i need to provide storage for electricity generated or can it be wired direct.

Apologies for not having a U-value for the house. The insulation level are below if anyone wants to see how well I plan to insulate it.


[wall insulation: 120mm xtratherm with 50mm poured cavity bead insulation Roof Insulation:100mm rockwool, layer multifoil, 37.5mm insulation plasterboard]

sydthebeat

quazzie

your roof insulation does not comply to minimum regulations....

who recommended multifoils to you?

as a BER assessor i would have to ignore the multifoil as an insulator as its not certified.

Quazzie

I actually read of that combination on here as a possible dormer roof insulation. I know the multifoil isn't certified but i was just planning on using it as an extra layer, What insulation would you recommend for a story and a half house?

sydthebeat

Quazzie2002 wrote: »

I actually read of that combination on here as a possible dormer roof insulation. I know the multifoil isn't certified but i was just planning on using it as an extra layer, What insulation would you recommend for a story and a half house?

minimum regs on slope = 130 Pu or PIR or similar, to achieve 0.2 u value

minimum regs on flat = 200 PU or PIR or similar, to achieve 0.16 u value

The multifoil definitley has insulative properties, however its very hard to quantify it...

Quazzie

Excuse my ignorance but Pu means?

sydthebeat

sorry for the acronymns quazzie

PU = Polyurethane............
PIR = polyisocyranuate......

basically these are comparable materials.. more commonly known by their branding ie kingspan or xtratherm....

sinnerboy

Quazzie2002 wrote: »

Hi,

I'm in the process of plans and pricing for the construction of my own first house. I've already decided on Geo-thermal heat pump linked to UFH as the way to go but am worried about some recent bad press they have recieved regards there allegadly fabricated eco credentials, due to the Electricity required to power them. So lately I've been toying with the idea of installing some Photovoltic solar panels with the sole use of powering the heat pump, therefore making it trully free and eco friendly. My problem is I am totally clueless regards anything electrical and would like some advice regarding (a) what size panels and Geo-thermal pump I'd need to heat a 3200sqft house (b) the initial cost of this system and (c) do i need to provide storage for electricity generated or can it be wired direct.

Apologies for not having a U-value for the house. The insulation level are below if anyone wants to see how well I plan to insulate it.


[wall insulation: 120mm xtratherm with 50mm poured cavity bead insulation Roof Insulation:100mm rockwool, layer multifoil, 37.5mm insulation plasterboard]

PV's are amazingly expensive . And you could problaby cover your entire roof with them and still not provide the power to run the heat pump .

Your wall spec is puzzling - will you have a 170mm cavity ? you will need a structural engineer to design the wall ties . and factor them then into the u value calcuation . do you know you can't get a cert for beads unless cavity ( for beads ) is +50mm ?

Syd is correct about multi foils - do not use

consider anything except cavity walls

• poroton
• solid blocks and external insulation
• timber frame
• icf's

( no particular order there )

You need a BER assesosr who is also an architect

Slig

I disagree with your last statement!!!!
Architects dont focus on the details!!! An Architectural Technician is a lot more appropriate for the job

sinnerboy

Being a tekkie myself :cool:.... I am inclined to agree

AckwelFoley

Forget about the idea of using pv panels to power a heat pump.. i just don see the math working.. the investment in the setting up of pv panels and the return is not a runner.

Perhaps unless you used an air to water heatpump with "inverter tec" which even tho its sized at say.. 11 kw its normal running is at about 4kw.

Quazzie

Your wall spec is puzzling - will you have a 170mm cavity ? you will need a structural engineer to design the wall ties . and factor them then into the u value calcuation . do you know you can't get a cert for beads unless cavity ( for beads ) is +50mm ?

I've also considered 60mm Xtratherm with 110mm bead insulation, of which I hear the latter is the most efficient. For wall ties I will be more than likely using 'snap ties' as commonly used in the construction of panel shuttering poured concrete walls, mainly because I have an abundance free to hand due to extras collected over the years by my Dad.

consider anything except cavity walls

• poroton
• solid blocks and external insulation
• timber frame
• icf's

I have to use Blocks because my budget is so tight and my Dad is a blocklayer so thats where I hope to make most my savings.

Quazzie

minimum regs on slope = 130 Pu or PIR or similar, to achieve 0.2 u value

Thanks for the information Sydthebeat. If i change my 100mm Rockwool to 150mm xtratherm used in conjuction with the 37.5mm insulation 12mm plasterboard what U-value would that give me? Would that be adequate. I understand it'd be above minimum regs but in your own opinion would be this classed as good insulation. I don't mind spending a but extra on insulation to save in the future. Plus if possible could you comment on my wall spec.

Slates

sinnerboy wrote: »

PV's are amazingly expensive . And you could problaby cover your entire roof with them and still not provide the power to run the heat pump .

Your wall spec is puzzling - will you have a 170mm cavity ? you will need a structural engineer to design the wall ties . and factor them then into the u value calcuation . do you know you can't get a cert for beads unless cavity ( for beads ) is +50mm ?

Syd is correct about multi foils - do not use

consider anything except cavity walls

• poroton
• solid blocks and external insulation
• timber frame
• icf's

( no particular order there )

You need a BER assesosr who is also an architect

What your objection to cavity wall construction sinner ??

smooth operater

Haven't been on this in a while....Anywho.......
Using p.v. to power the heat pump is a bit of a contradiction, u need the heat pump during the winter mainly, during which there is very little sunlight.

Try construct the house so its sealed, as much insulation as u can afford throw in a HRV unit, buy some solar panels for your hot water, and a nice efficient gas boiler

Bobs you uncle.....

sinnerboy

Slates wrote: »

What your objection to cavity wall construction sinner ??

After only 20 + years seeing it built i've lone ago arrived at the conclusion that brickies and blockies who have to contend with muck and wind and shaky scaffolding etc are either not inclined and/or not interested in installing cavity wall insulation correctly

mortar snots , bent or missing ties , missing retainer clips , large gaps between vertical joints in boards , mortar droppings like a festering sandwich fill between horizontal joints , missing ( entirely ) insulation behind cills and behind vertical dpc's , boards not placed tight and true to the internal leaf , stepped dpcs that are not actually stepped , crushed old fag packets used where retaining clips should have been .......... is what i can think of as typical - off the top of my head . All defects DRAMATICALLY affect the actual u-value vs the designed u-value .

timber frame walls - factory insulated
ICF walls
poroton walls
externally insulated walls
SIPS

all eliminate these defects

if you ( the OP I mean ) can do blockwork cheaply i advise the following

build 215 inner leafs - reason - walls during construction can be safely built inner leaf only . let ties stick out and use foil faced Kingspan/xtratherm/quinntherm . you can watch the board joints and can ensure to keep them ultra tight - foil tape the joints most particaulrly at corners . You can clearly see wall ties , stepped dpc 's are all present and correct . DO NOT ATTEMPT WITH 100 INNER LEAF - NOT ROBUST ENOUGH

then follow on with external leaf later over your flawless "silver machine" . you still need to supervise strictly to avoid mortar droppings . leave out every 4th block along the base dpc level to remove the occasional inevitable dropping .

sas

Better still would be to build single leaf 215mm and externally insulate it.

Twould be somewhat more expensive though.

sinnerboy

Really sas ?

In case of ext insulated wall ( a la MosArt ) once 215 wall is built .....

no stepped dpcs , heavy blockwork , wall ties etc .

just thick but light slabs of EPS ( adhesive fixed at MosArt ) and acrylic render over

I'm not "challenging" you but i am surprised

sas

sinnerboy wrote: »

I'm not "challenging" you but i am surprised

At the price part or the fact that I think external insulation is a good thing?

Quazzie

Would the 215 inner leaf not act as a heat sink therefore undoing all your good work?

sinnerboy

sas wrote: »

At the price part or the fact that I think external insulation is a good thing?

the price part

sinnerboy

Quazzie2002 wrote: »

Would the 215 inner leaf not act as a heat sink therefore undoing all your good work?

yes . no .

look here - Ireland 1st certified ( by PHI ) Passive house

http://www.mosart.ie/arch_passive_photos_cam.html

215 block + 300 EPS + acrylic render

sas

sinnerboy wrote: »

the price part

As you said its literally only EPS sheets but for u-values no better than 0.2 I've been quoted 100 + VAT per square metre (nothing cheaper). This is for the finished job i.e. insulation and render.

For me that's 41k. That's an awful lot for that u-value.
Plus you have to take account of the cost of building the 215mm wall.

Having said that, I believe you simply can't beat external insulation in terms of price for performance. My figures suggest I can achieve an external wall up and rendered to a u-value of 0.1 for no more than 70k.

Contrast that with the 2 quotes for ICF systems I got for 0.15 u-values of 75k and thats before I fork out the 50 per square for the renders. (Approx 360 square metres)

Slig

the most important thing about cavity walls is that no matter what you do there will be cold bridges, SINNERBOY I like your idea about the 215 inner leaf, its a pity cement board is so expensive as it would be easy to create a breathable cavity wall using this and thermally broken clips (for the old die-hards) Some good information on this thread. Like to see some feedback on poroton though, how is it working here?

sas

Slig wrote: »

Like to see some feedback on poroton though, how is it working here?

I was fully committed to building with the poroton T8. I even have footings in place for them i.e. 440mm wide solid rising wall.

I visited 1 site and thought it was a mess, the block work really was poor. I chalked this down to bad luck. I visited a second site which was only slightly better. Then i visited a third which was supposed to be using an eastern european crew that were quite experience with it. Again gaps all over the walls because its (apparently) very difficult to cut the blocks accurately.
This meant that my 0.18 u-value wall was likely to have several horizontal gaps filled with the plaster afterwards. I've also heard its gone up in price recently so I was looking at 75k just for the blocks. I'd still have the labour to lay them and the materials and labour for plastering inside and out.

It's too expensive, it's too hard to get right (in my opinion) and I can't see how you'd make any modifications afterwards (should you need to) given that there is no mortar in the horizontal joints.

I am also concerned by some of the advertising by FBT in several of the most recent issues of Construct Ireland. Namely, the claim that a u-value of 0.11 can be achieved with it. The best available poroton block is the T50 which gets you to 0.13. FBT are not interested in talking about externally insulating the T10 walls like the germans do. Also, the full page add. in the most recent CI says that poroton is passive house institute certified. If it is iI can't find it on the list of certified products on the passive house website.

I've looked at poroton, sips, timberframe, ICF and EWI and I reckon it'll be EWI or ICF (EWI is the current front runner).

Quazzie

Excuse my ignorance but what is EWI??

sinnerboy

external wall insulation

itsmedee

Quazzie2002 wrote: »

Hi,

I'm in the process of plans and pricing for the construction of my own first house. I've already decided on Geo-thermal heat pump linked to UFH as the way to go but am worried about some recent bad press they have recieved regards there allegadly fabricated eco credentials, due to the Electricity required to power them. So lately I've been toying with the idea of installing some Photovoltic solar panels with the sole use of powering the heat pump, therefore making it trully free and eco friendly. My problem is I am totally clueless regards anything electrical and would like some advice regarding (a) what size panels and Geo-thermal pump I'd need to heat a 3200sqft house (b) the initial cost of this system and (c) do i need to provide storage for electricity generated or can it be wired direct.

Apologies for not having a U-value for the house. The insulation level are below if anyone wants to see how well I plan to insulate it.


[wall insulation: 120mm xtratherm with 50mm poured cavity bead insulation Roof Insulation:100mm rockwool, layer multifoil, 37.5mm insulation plasterboard]

I am thinking the same for my new build (geo heating system). i am toying with the idea of this http://www.exmork.com/water750w.htm as i am lucky to have a river to the rear of my site,
I will need to do some more research, approx 2000euro to set up?
i will keep ye posted!

http://www.yourhome.gov.au/technical/fs49.htm

boardwalk

Spend the money for PV on a decent well and go for a water to water heatpumpe which is much more effective than air to water.