“The low-consumption model house reduces to one third the energy demand of the model house with the levels required by current regulations”
“The low-consumption model house produces 3000 kg of CO² less than the model house with the levels required by current regulations”
1. Improvement parameters:
The objective of this first part of the basic energy study is to model the monthly demand of 8 model houses, parameterized with 3 main variables:
1. Transmittance of opaque enclosures (facades, sanitary slabs, under roof, roofs, etc.). For the improved option, for example, a façade transmittance of 0.34 W / m2k and a cover transmittance of 0.15 W / m2k are valued. For the normative option, the minimum transmittances defined by the CTE DB HE1 are used for the geographical situation and for each constructive element.
2. Carpentry transmittance and solar factor. For the improved option, carpentry is defined with a U of less than 2 W / m2k, 4-12-6 and a Low-E camera. For the normative option (CTE quality) a glass equal to the previous one is established but without low emissivity camera and a U of 3.10 W / m2k.
3. Ventilation installations. For the improved option, a double flow system with static heat recuperator is established (with an estimated recovery of 50%). For the normative option it is calculated with an admission by aerator in the carpentries and hybrid or mechanical extraction, conventional solution to fulfill the state norm CTE.
2. Case study:
For the theoretical modeling of the 8 type houses the monthly demand calculation method prEN 13790 has been used. Below are the graphs of annual demand balance with monthly detail and thermal loads broken down as follows: U envelope (losses or gains through the skin of the building including carpentry) Ventilation (of health and natural) Solar (gains by solar capture by openings) Interior (interior thermal gains).
House type 8 Envelope U CTE / Carpentry CTE / hybrid sanitation ventilation with aerators in carpentry
The good orientation of the collecting holes added to a good dimensioning of openings allows us to have an important contribution of solar energy. This means that we can easily reach, without excessive increases in insulation, low consumption values (less than 30 kWh / m2 per year).
The consumption of the improved quality house (house 1) is reduced by approximately 50% compared to the CTE quality house (house 8). We observe that the most relevant parameter in the reduction of consumptions is the increase of isolation, although in the system of double flow has considered a recuperador of 50%, being able to increase easily in 80%. Another noteworthy fact is the little influence of the improvement in carpentry on consumption in the winter period; this is due to the significant reduction in the solar factor caused by the low-E camera, which leads us to deduce that in cases where we have a very large catchment area, large windows to the south for example, and the magnitude of gains by radiation are important in the energy balance, we can assess the lack of the low-emission chamber in the capture gaps to increase the contribution of energy by solar radiation to the balance.
As for CO2 production, the low-consumption option produces 3 tons less CO2 per year. To have a more enlightening comparison we have compared the consumption of standard houses to the consumption of a car: while the CTE level house consumes the same as 3 cars that make an average of 10000 km per year, the low consumption type house consumes the same as 1 car.