In southern Portugal, you only need heat for a few months in the year [January mainly].

But most houses are still unheated, even new builds.

Temperatures rarely drop to lower than 10 degrees, but frost is possible on a few occasions each year.

Days are warm [18 even in January] if sunny, but on cloudy days the temperature in winter can stay  down around 10-12 degrees.

 During the winter months, there is a lot of rain. Combined with lower temperatures, most Algarve houses have trouble with damp and mold.

Central heating, aside from the obvious comfort of it, keeps your house and possessions dry.

Underfloor radiant heat does this best, because the heat is evenly distributed, preventing cold spots where damp and mold would otherwise form.

The other big advantage is the lower operating temperature, which allows higher efficiency [less heat loss at the boiler], and is ideal for adding solar heating.

By using a water based system [as opposed to direct electric], any heat source can be easily retrofitted; electric storage [night rate is half price], pellet or wood burner, a high efficiency condensing gas boiler, heat pump,  solar collectors, or whatever comes next.

 Retrofitting an existing house with underfloor heat is a massive amount of work, but if you want to replace your floors anyway, and/or take out some walls, then it’s probably worth it. Since most existing houses have masonry flooring with no insulation below, trying to get them comfortable with an added on heat source is difficult or impossible. The floor will always be cold.

 How the work is done;

The old floor is broken out, and dug down about 20cm. this isn’t very hard, since slab foundations are unknown here, but it does make a lot of rubble to be disposed of.

A steel reinforced concrete slab is then poured in; this adds a lot of structural strength to the house too.

Insulation is laid on top, then the heating loops, and another layer of concrete fill.

On top of that the finish flooring is laid, which can be whatever you want. Tiles are traditional in Portugal, but you can have wood, carpet, or vinyl if you prefer. If you use wood, it will have to be a type of parquet approved for floor heating.

If you want this done in the Aljezur area, I can recommend the builders who did mine. Contact me.

Insulation;

I thought the hollow brick wall wouldn't be too bad; I was very wrong. heat wicks out and cold creeps in.

Aside from the bad efficiency, the cold interior walls cause condensation to form, which causes mould. lots of people struggle with that.

Newer houses are built with a layer of foam insulation between the masonry; this is required by law.

It's pretty good, but the foam is useless for acoustic insulation. I find that sound goes through the hollow brick like it wasn't there.

If you're renovating your interior, I recommend using 50 or 75mm of rockwool insulation, and a layer of plasterboard [sheetrock, gypsplaat, gesso]. Thermal and acoustic insulation, and new smooth walls. Easy to put in new power and data wires as you go.

If you're not renovating the inside, it's probably easier to insulate from the outside; this is a job known to builders here.

A 50mm layer of insulating foam is bonded to the outside walls, then stuccoed over with a thin layer of special cement, smoothed and painted. It looks just like the old outside wall.

A friend of mine who had this done reports the house as totally comfortable through the winter, and free of damp.

 Other heat systems;

Radiators, obviously. They operate at higher temperatures [70 / 80 degrees as opposed to 40], so require a hotter [less efficient] heat source. They take up space on your walls, and are [in my opinion] ugly. But they’re easy and quick to fit.

 Forced air; I don’t think anyone uses that anymore.

Radiant electric; costs a fortune to run, but very cheap to buy. Lots of people here use these heaters to take the chill off. Especially if they don’t have to pay the meter charges.

 Heat sources;

As I said above, once you have a water based system [floor heat or radiators], you have a choice of heat sources.

 Pellet burners;

Very popular, with good green credentials. There are some drawbacks though. The initial cost is rather high, and it can take years of use to recover it.

The fuel is generally cheaper than oil or gas, but varies a lot, depending on supply and demand. It comes in small sacks that have to be loaded by hand. Not as troublesome as firewood, but more work than electric or fossil fuels. You need ample sheltered storage area.

Possibly in future pellets will be available in bulk.

 Log burners;

The cheapest fuel, the most work. Firewood is delivered by the truckload at reasonable rates, or cut your own [if you have any forest]. In practice, central heating using a wood fire is tricky since the fire is hard to control accurately, and it’s vital not to let the water boil in the heat exchanger. But there are systems available.

The ash needs to be cleaned out regularly, and the fire tended every few hours while in use. Most people who burn wood for heat just have a simple stove of some sort in the house.

Uneven heat, troublesome, and takes up a lot of space. Cheap and cheerful though.

 Gas;

The most efficient of the fossil fuel options, since very efficient, mass produced boilers are available for reasonable prices. They’re very small too, and can be fitted into a broom cupboard.

Gas supply in the Algarve is by bottle [carafe in Portuguese]. The large ones, too heavy to handle by hand, are reasonably priced, and delivered. The small 12kg capacity ones can be exchanged at shops and fuel stations, but are exorbitantly expensive. Ok for cooking, but I wouldn’t use them for space heating.

Big fixed tanks that can be filled on site are the cheapest for supply, but the most expensive to install. If you put in one of those, you should be planning to stay with gas for a decade at least.

Oil; unstable prices, easy to store, delivered at short notice for around 89 cents per liter [2010]. The burners are powerful but fiddly. Systems tend to be a bit smelly, so should be in an outside room. As far as I know, high efficiency systems are not available.

 Solar home heating, the holy grail;

With all the sunlight we get in southern Europe, it really should be possible, and it is.

Just ask any of the companies that want to sell you a system. For €10,000 [and that was in 2008].

For that money, you’ll get a system installed with 8 M2 of heat gathering panels, a state of the art Solvis reservoir and control system, that could supply [they claim] up to 80% of your thermal energy needs through the year.

The salespeople are pretty slick, too.

 That price does not include a backup heat system [for the other 20%] or the heating loop [radiant floor heating or radiator installation]. You pretty much have to have floor heating to get anything from the sun, radiators just operate at too high a temperature.

 Ok, if I break it down, the truth is that the yearly thermal load includes domestic hot water [DHW], which for about 9 months of the year can be easily achieved with a system that will only cost you a few thousand.

The other €6000 or €7000 will get you some interior heating, saving you several hundred per year.

 The problem is the high prices charged here. €1000 for a 2 square meter collector is nuts. I can get a near equivalent for as low as €400 from a supplier in the Netherlands.

The clever part of the system is the Solvis heat reservoir and control system. But that part is €6000 alone. And it’s only 600 liters.

That will keep your house warm through the night, but if you have a cloudy day, you’ll be on fossil fuels again within a day.

According to my calculations, in winter a 100 M2 house will need about a ton of stored hot water to stay warm through 24 hours. Of course there are a lot of variables, like heat loss and so on, that are particular to your house.

Why do they make them so small? They’re made in a factory in Germany [a carbon neutral factory, if you want to pay for that]. They need to be shipped, stored, and then fit through an average doorway to be installed.

 That is the high end system, and there are lots of cheaper ones, each with their own sales pitch; but the bottom line is the same. What we get is very little heating at a very high price.

 The accepted wisdom is that solar heat is a great idea, but so far, unpractical economically.

 Unless you build your own.

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