The thermal insulation is what counts, not the conduction capabilities of the bricks

Author: Vértesy Mónika
2011-04-22

A major part of the housing stock in Hungary was built of B30 blocks, which have roughly three times worse thermal conductivity than the values allowed by the standards nowadays. Still, we can not say that the B30 block should be considered as bad masonry material, it just has to be covered with a thick thermal insulation layer. Let’s see a concrete example!

I made the following example of calculations for this year’s seminar, which is an informative event held annually for those who are laymen and about to begin a consturction. The feedbacks and our experiences are really good, the next seminar is planned to be held in March or April of 2012.

Until then, let’s see this family house designed by é z s é. How do heating expenditures change depending on whether we use B30 or Porotherm NF blocks and also depending on the thickness of the thermal insulation?

house design in Dunaharszti

We consider all the other factors constant. The one-story building has a useful floor area of 132 m², the proportion of the bounding surfaces and the full volume is 1,2, so we are dealing with an average family house. The desired interior temperature is 20°C, the heat transfer coefficients: the floor, 0,35 W/m²K (standard: 0,5 W/m²K); the roof, 0,14 W/m²K (standard: 0,25 W/m²K). The door&windows will be made with a two layer glazing with low-E coating and argon filling inside, which have a U-value of 1,1 W/m²K. The minor part of the house will have air heating with a wood-burning fireplace, the major part will be heated by a condensational boiler and radiators, so not the best solution ever…

Initial condition: B30 block masonry without thermal insulation

The price of the wall was not taken in consideration in this case, but it is worth to know that it takes more time to build a wall from B30 blocks as the size of the block is smaller, not to mention that the costs are a bit higher than in the case of choosing the Porotherm tounge and groove blocks. However, the B30 block has a greater weight, which plays an important role in reducing and delaying the environmental temperature.

So, we look at the B30 block wall without insulation as the initial condition, this way the annual heating expenditures would be approximately 330 000 HUF, counting with a gas price of 160 HUF/m³.

	B30	B30 + 5 cm	B30 + 16 cm
U - value	1,52	0,52	0,22
Unit price of the thermal insulation	no thermal insulation	8300 HUF/m²	10500 HUF/m²
wall surface	117 m²	117 m²	117 m²
investment costs	0 HUF	971 000 HUF	1 229 000 HUF
heating energy demand	148 kWh/m²/year	84 kWh/m²/year	64 kWh/m²/year
annual saving (with 160 Ft/m³ price of gas	initial condition	144 000 HUF	182 000 HUF
payback time	initial condition	6,7 years	6,7 years

Insulation variations for B30 block

By applying 5cm of thermal insulation, a spectacular result can be achieved, the heating costs are reduced with 42% and 144 000 HUF is saved annually. The investment costs of the insulation are paid back in 7 years. (You can find the U-values and prices of arbitrary chosen masonry materials and thermal insulations in our wall-construction calculator.) The reason why the result is so spectacular in this case is the really bad initial condition. With an additional 11 cm of insulation (so with 16 cm in total) we can not achieve such a sharp change, but we still recommend this solution. Why is that? Take a look at the price of the thermal insulation! The additional 11 cm of insulation only means 2200 HUF of additional costs, as we have already paid once the expenditures of the labor. The only thing that changes is the price of the material. The payback time is the same in both cases, but after these 7 years the greater initial investment will do good for us, as we were able to reduce the costs of the heating by 50%!

What about the heating costs with a more up-to-date masonry? (Porotherm 30 tounge and groove block)

The Porotherm 30 tounge and groove ceramic block has the same insulation capability as the B30 block with 5cm of insulation. However, it still does not fulfill the requirements of the current standards without additional thermal insulation, not to mention the upcoming tightening of the building energy regulations.

Nevertheless, the greatest moral which can be read from this comparison is the following: if a sufficient amount of thermal insulation is used, the difference between the thermal conductivity of the blocks becomes more and more vanishing.

	PTH 30 N+F	PTH 30 N+F + 5cm of insulation	PTH 30 N+F + 16cm of insulation
U - value	0,5	0,3	0,17
Unit price of the thermal insulation	no thermal insulation	8300 HUF/m²	10500 HUF/m²
wall surface	117 m²	117 m²	117 m²
investment costs	0 HUF	971 000 HUF	1 229 000 HUF
heating energy demand	83 kWh/m²/year	70 kWh/m²/year	61 kWh/m²/year
annual saving (with 160 Ft/m³ price of gas	initial condition	29 000 HUF	49 000 HUF
payback time	initial condition	33,4 years	25 years
Annual savings compared to the masonry from B30 block with the same insulaton!	146 000 HUF	31 000 HUF	7 000 HUF

In our following article we will examine the types of insulations and where to use them on the house. Is it possible that the EPS facade insulation have a competitive rival?

How to choose masonry if the sound-proofing capabilites are also an important factor besides thermal insulation?

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