How to choose energysystem and insulation?

07/26/2010 - 17:31

Hello All! I am new to this community but has already learnt a lot studying earlier posts. We live permanently in Italy since a year and are renovating an appartment of about 200 sqm. It´s in the historical center which means thick stone walls and a strange shape of the appartment. The outdoor temperature is very rarely beyond freezing, most days in mid-winther are around 5 - 10 degrees. We are happy with our builder and our architect but since they are both italian their concern and knowledge about energyquestions are not as profound as their knowledge about �� laws and renovations in the "centro storico". Underneath the appartment there is the ground on 50 sqm, cellars on 70 sqm and neighbours (warm appartmens) on another 70. There is 120 sqm roof. Since we are totally renovating there are many choices to be done. We are aiming to have underfloor heating. The energy will come from a gas caldaia or an air/water heatpump. We will also install a termocamino and a heatbank. Plus a bit of solar energy - might be allowed says the authorities. We are now worried that the heating will cost a lot of money due to the fact that another client in a similar sized house was spending 500€/ month in winther. We want to put 8 cm insulation in the roof and have 3 cm under the floorheating where there is warmth below, and 6 cm where there are cellars below. On the part where there are ground below we might use regular radiators since this is an area where we will have lower temperature. We hope to spend less than 1000 € per year on heating. I will be very happy to have input/suggestions for changes/improvements. I am especially curious if the thicknesses of the insulations described above are O.K. Thomas

Topic

Property

Renovating

Location

Abruzzo

Comment

Put the highest amount of insulation that you can to cut down the energy cost. If using an air/water heat pump with a heat bank, then you can be secure to temp of -20c. Would suggest you get your geometre to give you a thermal analysis of the property with different insulation levels.

Hi Thomas, I'm also new to this too. We installed underfloor heating powered by a) solar thermal, b) wood stove and as a last resort c) a gas caldaia. All the heat goes into an accumulator which lives in the cantina. So far we've kept the house warm and have hot water using just sun and wood which we have masses of. We try never to use the gas as you can get through hundreds of euros in days. The whole system takes a bit of getting used to and you have to watch the weather and plan ahead. If we just used as much heat and hot water as we wanted, the gas would kick in to top up but we have turned the gas boiler off and restrict heat to two rooms and shower room+towel rail. That way we run the system for nothing. If it is raining we hardly get any solar so have to light the stufa much earlier in the day. In summer we have to get rid of the solar panel heat into rooms we're not using, and use up the hot water (which seems like a waste but in fact was heated for free). It takes 3-4 hours to heat the floors and days to heat ice cold walls when we've been away but the system works beautifully once you get the hang of it, and it is virtually free to run. There are a couple of little electric pumps that we'd like to power by PV solar one day when we work out how to. You need to put as much insulation in above and below as you can. We put 12cm in the roof and would have done more but roofing company couldn't fit it. UK regs for roofs are 15cm Kingspan. Under the floor you need to keep the heat in as long as poss. We wanted 30cm polystyrene if we could, but the plumber had a system of 3cm polystyrene and 12cm clay beads below that and wouldn't accept the need for more.We will hang curtains up at the windows and doors in winter and use them to keep the heat in. It all helps. We also put these large plastic dome things over the earth floor before laying the base concrete. Hopefully they create some sort of airgap/insulation? It certainly isn't the easy gas central heating system that we're used to but there are no bills and we're willing to think about what we need and manage the system. The only thing we haven't got the hang of is leaving a big enough log in the stufa when we go out at night. It always burns out before we get home and on a cold, rainy day the floors take the heat out of the accumulator pretty quickly without solar help. Apicoltrice

I will try to beef up insulation a bit but there are also the questions of ceilingheight and how much insulation the italians will put in without arguing to much. There is no geometra involved and I haven´t discussed thermal analysis at all. Apicoltrice, your system seems to be similar to the one i am aiming for. I wonder about your size of house and size of accumulator. It seems sad that you keep returning to a cold house after a night out. I hope to have a 500 litres tank. Does your stufa produce hot air but no hot water? I also wonder if it is better to put the gas caldaia "after" the accumulator so that it will only heat water if it is not already hot enough from solar and wood energy. Or if would be better to have the caldaia heating the water in the accumulator as well. It seems to me that the first alternative would consume less energy if the caldaia is smart enough to handle the situation of heating only when water is not already the right temperature (also depending on whether it´s going to heat the floors or if it´s for the bathroom.

Sorry about the long gap in replying but have been in Italy where we don't have internet yet. Our house is 140m sq, but in 3 separate buildings. The accumulator is about 2m high by 90cm wide including the insulation. I can't remember how many litres. The stufa produces hot water not air and the gas caldaia is after the accumulator so it only kicks in if it has been raining all day or we haven't lit the stufa, but we have actually switched it off for economy! Ok, we can easily switch it on if needed. The reason for sometimes returning to a cold house after a night out is that when the stufa has burned all the wood and we aren't there to load it, if it has been a rainy day, the accumulator loses its heat and the gas isn't taking over as we've switched it off. This winter we will have massive logs that will keep burning while we are out. Logs heat the water at about 65- 80 deg C. In summer, the 4 solar panels make too much heat. We've been watching the temperature from them this week going in from 40 deg C early in the day, up to 85 deg at midday. You can tell from the outdoor temp that there is too much heat going into the accumulator and we turn up a few floors in various rooms before it actually boils over. We always have the shower room and rad on at 24+ deg and that wastes the heat nicely while being cosy on the feet late at night. The system is from: www.sonnenkraft.co.uk We're pretty happy with the system as it supplies all the hot water we need and the underfloor heating keeps the chill off everywhere, but in proper cold, wet weather we do need a couple of extra stufas - one in each building, for real heat. It would transform the underfloor heat if we would use the gas which chucks the heat out quickly, but the aim is for free heat, so we compromise. I wonder how much the cost of installing two more stufas will be compared with just using gas???? But once installed, the stufas will heat us with our free wood. Hope all goes well and I'd be happy to offer any more info if needed.

Abbruzo, Your point about gas before or after the accumulator hints that you are still thinking about the old ways of doing things. A heat store is full of dirty water with EVERYTHING - OK not the solar coil - connected directly to it, gas boiler included. The clean hot water is extracted via an internal coil or an external plate heat exchanger. As you will almost never use the gas boiler there is no need to worry about optimising it - just remember that the heat store should be vented and therefore the gas boiler will be the vented, heat only type and, from my experience, often not quite the one your plumber fancies. As you are not on the ground floor I suspect you are not going to be keen to lug tons of wood around so the heat pump sounds like a good plan and with one of those and some electric water heating you might not need any gas at all! I find that under-floor heating saves a fortune by producing tolerable temperatures and warm feet so I would put it under all floors except bedrooms where faster response times are better.