underfloor heating

by **La Dolcevita** Mon May 27, 2013 3:35 am

First topic message reminder :

We're looking to put underfloor heating in to our property as it seems to be the most efficient (can't bare the cold) and most economical long term - our architect has put a spanner in the works as he has said that it can take a few hours to warm up/cool down. Has anyone had any experience of underfloor heating - thoughts/comments appreciated

by **Geotherm** Tue Jul 30, 2013 3:44 pm

If there was not enough land, then a borehole is basically the only alternative, so I see your point on that issue. We try to always avoid that route if we can, as it is the most expensive. If the client had metano available, then unless they were definate with wanting a heat pump, I would not recommend one. Cost recovery with a normal ground loop instalation, would be approx 7 years minimum, probably double that with boreholes.
As a example, we installed in Tuscany 2x11Kw GSHP's in a 350 sq mtr house, with no loft insulation or double glazing, with a 500 ltr DHW tank. The 2 loop excavations were 160 mtrs each, so not a phenomemal length.
There are quite a few companies that have recently entered the market, that only want to do boreholes, as there is far much more money to be made that way.

by ourtoscana Wed Jul 31, 2013 5:32 am

We also looked at the excavation solution but there were stability issues given that the land was terraced on a hillside. The customer wanted to adopt a green solution but the numbers simply didn't add up and so we stuck with methane.

When you did the two 160m excavation per loop, what kind of section did you dig?

I also have another project right now where we are offsetting the estimated annual consumption of the heat pump with photovoltaic cells. Have you ever experimented with such a combination? Thanks

by **Geotherm** Wed Jul 31, 2013 7:37 am

ourtoscana wrote:We also looked at the excavation solution but there were stability issues given that the land was terraced on a hillside. The customer wanted to adopt a green solution but the numbers simply didn't add up and so we stuck with methane. When you did the two 160m excavation per loop, what kind of section did you dig?I also have another project right now where we are offsetting the estimated annual consumption of the heat pump with photovoltaic cells. Have you ever experimented with such a combination? Thanks

In that scenario, there could have been the consideration for what are known as compact collectors. More expensive than the normal loop, but less than a borehole.
http://www.geotherm.it/Scambiatori_geotermici_compatti.html

With the 160 mtr trenches, they were 1.2 mtrs wide x 1.3 deep. Minimum seperation of 3 mtrs. Each contained 4 probes with 30cm spacing.

Re the photovoltaic, yes we have a few projects operating with those as well. If you have a look at the examples and click on the images, then you will see a number have PV as well. We are finding that quite a few of our clients are changing to the ENEL BTA3 solely for the heat pump, as the rates are a lot less.

http://www.geotherm.it/Esempi_impianti.html

http://www.enel.it/it-IT/clienti/enel_servizio_elettrico/tariffe_per_la_casa/tariffe_per_usi_diversi/bta3.aspx?it=0

by **Gala Placidia** Wed Jul 31, 2013 1:09 pm

This is becoming a most interesting thread, full of detail and technical information. I should become a "sticky" for future reference.

by Sagraiasolar Wed Jul 31, 2013 1:59 pm

ourtoscana wrote:I also have another project right now where we are offsetting the estimated annual consumption of the heat pump with photovoltaic cells. Have you ever experimented with such a combination?

I have a modelled all the possible energy sources versus the energy requirements over the year. The idea is to design heating solutions using multiple sources and to make sure the energy stack always exceeds the seasonal demands. The result of tweaking all the variables appears on a graph and the likely cost of running the system is calculated at the same time. The PV + heat pump curves are interesting in that I have added an extra line for 'PV x COP' which tells you how much free energy is available via the heat pump at various times of the year. What this highlights is that there is a seasonal miss-match as the PV panels output in winter is about a third of the panels rated output. Don't let that put you off though. If you have a 6kWp array putting out 2kW then on a COP of 3 say, that is a handy and free 6kW from a heat pump - nice.

by **ghiro** Wed Jul 31, 2013 4:13 pm

ourtoscana wrote:The idea was to take the internal temperature down to about 23°C to 24°C range using a Buderus Logatherm WPLSODU with a shell cooling parameter of 8.7 KWh/m2 year over about 400smq of net floor area.

Strange. Just what I was thinking to myself earlier today! Very Happy

by ourtoscana Wed Jul 31, 2013 5:41 pm

That's really interesting Sagraisolar and your point on the 2kw makes sense. I guess the main problem for me is that the 6KWp array is hitting its full potential during the warmer months when the heat pump doesn't operate. Enel will give you peanuts for buying back this excess energy based on the new Conto Energia scheme? Am I missing something here?

by ourtoscana Wed Jul 31, 2013 6:12 pm

Ok Ghiro I got carried away on the jargon ... point taken!! ciao

by **Geotherm** Wed Jul 31, 2013 6:23 pm

Just to clarify a few points on the electricity usage, mainly on ASHP units. The EAN standard is based on a +7C outside air temperature, with either a 35C underfloor output, or a 50C rad output.
These are nominal figures, but for a 10Kwh output ASHP pump, it would consume circa 2.7Kwh @ 35C output, or 3.1Kwh @ 50C.
Reducing to a sub zero temperature, then there is the possibility of the electrical backup heaters cutting in @ either 3/6/9Kwh depending on the setup of the unit.
You also have to take defrost cycles into account.

by ourtoscana Wed Jul 31, 2013 6:27 pm

Thanks for that Geotherm. Do you know what the values would look like for say -5°C to -10°C range?

by **Geotherm** Wed Jul 31, 2013 6:33 pm

I have all the data for the full range of the IVT Air pumps, but cannot put them on here as they are PDF files. PM me with a email address and I will send you them.

by Sagraiasolar Thu Aug 01, 2013 3:59 pm

ourtoscana wrote:That's really interesting Sagraisolar and your point on the 2kw makes sense. I guess the main problem for me is that the 6KWp array is hitting its full potential during the warmer months when the heat pump doesn't operate. Enel will give you peanuts for buying back this excess energy based on the new Conto Energia scheme? Am I missing something here?

I'm afraid it is peanuts. Unless one pays lots of tax in Italy the PV game has pretty much died. Where one could design ZERO COST energy systems I think just low cost is all we can hope for now. The totally off-grid theme is not quite viable yet in my view but getting towards there and looking very interesting with some excellent modules to manage it all. It's the batteries that kill the deal as they will expire at an average cost of €1,000 a year and again there is that seasonal miss-match. If anyone would like to see the full exploration of this idea I wrote it up in the last Heating Newsletter.. just email me on heatingitaly at gmail.com and I'll send it to you.

by ourtoscana Thu Aug 01, 2013 4:10 pm

Your comment Sagraiasolar confirms my doubt. Better off using the PV money to invest in better windows or wall insulation and minimize heat loss.

by **Geotherm** Fri Aug 02, 2013 7:44 am

ourtoscana wrote:Thanks for that Geotherm. Do you know what the values would look like for say -5°C to -10°C range?

This is best I can show you at the moment. You need to click on the link and then on the download PDF file, you will get the basic info from the brochure.

http://www.geotherm.it/Pompe_di_calore_aria-acqua_IVT_Air.html

by ourtoscana Fri Aug 02, 2013 11:29 am

Thanks for the basic specs Geotherm. Perhaps there's a graphic representation of the performance curves somewhere?

by **Geotherm** Fri Aug 02, 2013 3:18 pm

From a earlier answer to you!! These are all graphs.

I have all the data for the full range of the IVT Air pumps, but cannot put them on here as they are PDF files. PM me with a email address and I will send you them.

by **Geotherm** Wed Aug 07, 2013 3:38 pm

This is probably of more interest to Sagraiasolar or Ourtoscana, but may interest others who are technically minded!!
The reports are from the Energy Saving Trust in the UK for field trials on heat pumps. The last report was only released yesterday and is very interesting , as it shows a lot of improvements on the original installations.

Will probably be boring for many of you scratch

https://www.gov.uk/government/publications/analysis-from-the-first-phase-of-the-energy-saving-trust-s-heat-pump-field-trial

http://www.energysavingtrust.org.uk/Organisations/Working-with-Energy-Saving-Trust/The-Foundation/Our-pioneering-research/The-heat-is-on-heat-pump-field-trials

by ourtoscana Thu Aug 08, 2013 5:35 am

Thanks for that Geotherm! This comprehensive study that looks at real data and answers a lot of questions for me on the real performance of the heat pumps. Any idea where I can pick up a hard copy? Thanks again

by **Geotherm** Thu Aug 08, 2013 6:31 am

ourtoscana wrote:Thanks for that Geotherm! This comprehensive study that looks at real data and answers a lot of questions for me on the real performance of the heat pumps. Any idea where I can pick up a hard copy? Thanks again

No idea about the hard copy, as there does not seem to be a purchase link. May be worth a email to them to see if one is available, otherwise the only other option is to print it all out.

p.s. Have emailed the graphs to you.

by **Gala Placidia** Thu Aug 08, 2013 6:49 am

Now, if you think that you have seen everything there was to be seen, now look at these charges planned on solar energy by the Spanish government.
solar charges
Now, the trouble is that these measures are contagious, particularly when they are aimed at collecting extra money Crying or Very sad

by mlinsin Sun Nov 22, 2015 5:34 pm

Hi, I am new to the board, great info here.

We were also interested in underground heating and our architect had 2 "arguments" against it.

1. The floors (1st and 2nd floors) have to have a certain strength / thickness to handle the additional weight of the water. Is anyone aware of these?
2. We were then considering a mix of radiators and radiant heat
He said that would make the heating system more complicated because now we would have 2 different water circuits for the system, one for the radiators and one for the underground heat.
Again, anyone aware of this?

My last question:
We are planning to use old terracotta tiles from the original building. These tiles are very thick (thickness of a 2 Euro Coin)
Is it even feasible to get radiant heat through these kind of tiles?

Thanks

Markus

by **Geotherm** Sun Nov 22, 2015 7:09 pm

Hi Markus.

Are the floors being relaid, to conform with earthquake requirements?

If it is a mixed type heating system, then it should just require a buffer tank and a mixer valve to smooth the temps out. Not complicated at all.

With the radiant floor, because it operates at lower temperatures, then no problem. Just realise you will not get instant heat and a geothermal system is a 24/7 operation.

by mlinsin Sun Nov 22, 2015 8:29 pm

Geotherm wrote:Hi Markus.Are the floors being relaid, to conform with earthquake requirements?If it is a mixed type heating system, then it should just require a buffer tank and a mixer valve to smooth the temps out. Not complicated at all.

With the radiant floor, because it operates at lower temperatures, then no problem. Just realise you will not get instant heat and a geothermal system is a 24/7 operation.

sorry, I voted by accident on your post, I thought it would collapse the response :-)

The ground floor doesn't even exist today so it is created from scratch.
We did ask for a seismic evaluation of the building and we have a structural engineer involved.

What is a mixed type heating system? Keep in mind, we are just at the beginning so many decisions have not been made yet which I guess is a good thing.

What I hear you say is that because radiators and underheating work on different temp. levels, we would include a buffer tank which brings the temp down and the valve would then mix the water of diff. temps to bring the temp for radiant heat to the required temp?

Is your last answer the answer to the tile thickness question?
So radiant heat can go through the thick tiles as long as we don't expect this to happen in a few hours, right
A 24/7 system means you have to run it all the time? Can you not switch off a geothermo system?

For the next years, we will not even live there in the winter, just in the summer as a vacation home. But in 10 years or so, we plan to retire there

Which of course brings up another question: With all the technology changes happening, should we maybe go for a simple solution now (natural gas) and wait out to install a more sophisticated geothermal system?

thanks
Markus

by Sagraiasolar Sun Nov 22, 2015 9:04 pm

Ha ... just proves my point that architects are behind the curve.
A buffer tank has no problem with mixed outputs (rads + floors) and IMHO you want to keep them separate anyway so a different pump for each controlled by progstats does that neatly.
The best solution for you is UFH on the ground floor - very economical and just plain nice to live with. For bedrooms it used to be rads (fast response times and cheaper) but to be heat pump friendly I favour fan coils which are even faster and are happier with lower temps and so more efficient. I know UFH is often used in bedrooms too but personally I really hate sleeping over a heated floor and anyway if you are well heated downstairs the floors above get pretty warm already. If your man has designed the floors so marginally that a few kilos of pipes would collapse them I wouldn't even go upstairs at all. As for the thick tiles, they heat up much quicker than you'd imagine... when testing the floor circuits you take your shoes off and you can tell in 10 minutes if a floor has just gone on. Transmission on old stone houses can be a bit marginal so make sure your architect has done his calculations carefully.

by **Geotherm** Sun Nov 22, 2015 9:40 pm

mlinsin wrote:
Geotherm wrote:Hi Markus.Are the floors being relaid, to conform with earthquake requirements?If it is a mixed type heating system, then it should just require a buffer tank and a mixer valve to smooth the temps out. Not complicated at all.With the radiant floor, because it operates at lower temperatures, then no problem. Just realise you will not get instant heat and a geothermal system is a 24/7 operation.
sorry, I voted by accident on your post, I thought it would collapse the response :-)

The ground floor doesn't even exist today so it is created from scratch.
That is no problem.
We did ask for a seismic evaluation of the building and we have a structural engineer involved.
Good, he will probably know a lot more than the architect.

What is a mixed type heating system? Keep in mind, we are just at the beginning so many decisions have not been made yet which I guess is a good thing.
See below

What I hear you say is that because radiators and underheating work on different temp. levels, we would include a buffer tank which brings the temp down and the valve would then mix the water of diff. temps to bring the temp for radiant heat to the required temp?
Correct

Is your last answer the answer to the tile thickness question?
So radiant heat can go through the thick tiles as long as we don't expect this to happen in a few hours, right
A 24/7 system means you have to run it all the time? Can you not switch off a geothermo system?
Yes, you can switch off the geothermal system if you want, but these systems are designed to run at their most efficient on a 24/7 basis. You can do a heat reduction on the flow temperature overnight on a timer.

For the next years, we will not even live there in the winter, just in the summer as a vacation home. But in 10 years or so, we plan to retire there

Which of course brings up another question: With all the technology changes happening, should we maybe go for a simple solution now (natural gas) and wait out to install a more sophisticated geothermal system?
Simple now, advanced later.

thanks
Markus

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