Saving energy in a house just bought

Hi to all
We are about to buy and omd house and needs to be completely refurbished.
We would like to receive assessment about all kinds of energy saving systems
Now that we are rebuilding it we would like to get perfectly insulated before we move in.
Thx for your time

The most important part is that walls, doors and windows have thermal isolation.

I have two solar panel, one for sanitary waters, and another photovoltaic. Heating is a mix of air conditioning and a pellet stove.

I live in Portugal and my monthly electricity bill is 50€. On winter I also spend monthly 20€ on pellets.

Portugal is not a cold country but electricity prices are among the highest in Europe. My brother in law, with a similar house, spends 300€ on winter months and 80€ during summer

I use OH to increase savings. Heating is segmented in several zones, presence control limits heating, temperature and humidity sensors help manage heating and dehumidifier targets automatically


Should windows be double or triple glaced? Is there much difference?
Any additional kwh being saved is worth

We have heard about pellet stoves, most of them are Spanish or Italian manufacturers, any special recommendation on any particular brand?

hi there,

energy saving depends heavily on the climate you’re living in. :wink:
But, the most important part is not electric/smarthome relevant:

  • insulation
  • insulation
  • insulation

Then comes the rest like:

  • what kind of heating system
  • how to (smart) heat/vent your home
  • how to use smart devices to (pre-)heat some devices in times, where energy is cheap
  • etc

As I also renovated an old house 10 years ago, a short description, what we’d done (living in the south of Germany: cold winters (normally down to -10°C) and mildly hot summers (normally up to 32°C):

  1. insulated the 30cm brick walls with 15cm of mineral wool and wooden structure before
  2. insulated the cellar walls and ceiling
  3. insulated the attic floor (non-living, too small)
  4. rebuild the complete electric installation (using KNX for all actuators: light, outlets, blinds, etc.)
  5. rebuild the complete water installation (making dummy connection for a later option to integrate rainwater-tanks for non-drinking water)
  6. rebuild the heating [1]
  7. installed a central venting system
  8. completely “smarthome” the thing

[1] heating
For the heating we opted to a combined “three-way” heating: main heating comes from solarthermic panels (20m2), which heat up the solar stratified tank (1700l). If there’s no or not enough sun for a few days, we can also heat up the tank with a wood-buring oven, which has a water sack going to the tank. And if we are too lazy to put wood in, we still have the “old” (20+years, but efficient gas condensing boiler) gas stove, which still works. Works as intended without a flaw.
We replaced the old convector heatings with floor heating in all rooms and normally if the tanks are at about 60+°C it lasts for at least 2-4 days (winter vs summer). of course in summer the tanks can go up to 90+°C and in winter they rarely come up to 70°C from the sun.
Would I still use solarthermic heating instead of a more powerful PV system and heat pumps? I don’t know, 10 years ago PV was not that potent (and more expensive) as it is now, perhaps you could go straight for heat pump, if your roof has enough space for a 12+kWp PV system.
What I do to save energy with heating is to:

  1. tell, who is home with calender entries (office/school-timetables, homeoffice, family holidays…) and presence detection and thus
  2. use the room thermostats to heat up the used rooms and let them chill a bit with non used ones
  3. tell the gas boiler to stay put (e.g. tell the Wifi-Plug: OFF) in the morning, if it’ll be a sunny day

And since a few weeks, we used the rest of the (South-oriented) roof - and part of the north side) for a PV system (12.2 kWp) and this helps us to save energy also - with the help of an EMS (ask @mstormi) to load our BEV, washing mashine, dish washer, whirlpool, …

There IS a hell of a difference. In Austria and Germany double glass is either not available - or more expensive than triple glass. Together with the right insulated window frames, it makes a HUGE difference. we have a huge southern glass front and it keeps the heat out in summer and in in winter! :wink:
our gas consumption is only 1/4 (or less) of that before.

I personally don’t like pellet stoves. For one, the burn CO2 (even if the industry claims it is CO2-neutral, it’s not. We need woods and if a tree falls and is not used, it emits a maximum of 60% of the CO2 it consumed while growing. And the pellet industry not only uses “left overs” for pressing pellets, they need grown trees to be able to meet the risen demand). And they also emit other gases like NOx and SOx and fine dust. So, if you are in planning consider a heat pump.
Heat pumps are efficient and in combination with a PV system save you a lot of money. Plus: they don’t need space for pellets or stuff. For us, we also think of throwing out the gas and wood boilers and use a heat pump.

from what it seems, you are at the beginning of planning. I don’t know, where that house is located, but I guess there’s energy consultants all over the world. in Germany you even get them (partly) paid for, and that’s what I recommed highly to to: Contact one and calculate all your plans and their ideas to get the best solution for your house and budget.

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I think in the EU when you buy a house, the seller must provide you with an EPC (Energy Performance Certificate). This looks like the certificate you get when you buy a new appliance or a new car, with different coloured bars green through red showing the rating A thru G. Most likely the existing house scored an E thru G. So find the survey company that issued the EPC on your house and ask them to advise you about what actions you need to do to raise the EPC rating to a B or C. For an old house it will be impossible to raise it to an EPC A rating…

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The economics on that changed drastically in those 10 years. Technologies converge.
Thinking systemic (not HVAC vs power vs mobility), today the most economic and climate friendly heating solution is to put as many photovoltaic panels on top of your roof as possible and get a heat pump.
Solar thermic is only of benefit in winter for heating. With PV you make better use of your roof and investment all year long, saving on electric power as well in terms of both, CO2 and money (+ think EV).


I use double windows but in my town the temperature rarely goes below 10C otherwise I would have opted for triple

Regarding the pellet stove it was more a wife’s request than a technical choice. I use an Ecoforest model without water heating. It connects nicely to OH using the http binding

My house is a two-flat villa with E/W windows, each floor with approximately 85 sqm, and we are 2 persons

Solar panel has a 300L water deposit with electric resistance (managed by OH). PV system has 3 panels, 450W each, and no battery. This one is not connected to OH, I’ve opted to contract electricy with daily/ nightly cycle so that energy cost is practically the same at any hour

There are many different ways to save energy in a house just bought, such as:

Reduce your electricity costs by turning off lights and appliances when they are not needed.

If you have air conditioning installed in your home, consider installing programmable thermostats that can automatically adjust the temperature based on when you’re home or away.

Choose low-flow showerheads and faucets that use less water without compromising performance or comfort.

Install energy-efficient lighting throughout your home, including halogen lamps and compact fluorescent light bulbs (CFLs).

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