Environmentally Friendly House Designs

In this article, we will discuss the different strategies for design in the construction of sustainable homes. The aim is to achieve a real estate stock that is efficient and environmentally friendly.

Passivhaus Standard: Efficiency and Sustainability Taken to the Extreme

If we talk about house designs that are environmentally friendly, we inevitably have to mention the Passivhaus standard. The standard aims for the construction of buildings that minimize energy demand, ensuring that their construction has the least possible environmental impact.

A passive house is one that achieves high thermal comfort inside while using the least possible energy. It is based on the principle of energy conservation, emphasizing and paying attention to the building envelope.

The Seven Basic Principles of the Standard

• Orientation of the building. This involves orienting the house in a way that maximizes solar energy use. In very hot climates, orientation should help in preventing overheating of the envelope, and additional measures should be taken to protect against radiation).

• The building envelope must have a high degree of thermal insulation, as the idea is to conserve interior energy as much as possible and minimize losses.

• Special emphasis should be placed on controlling thermal bridges, as they are the weakest part of the envelope through which a considerable amount of energy can be lost.

• Implement a design that has special control of unwanted air infiltrations. In a passive house, all air infiltrations necessary for proper ventilation of the interior environment must be controlled, to ensure a sufficient ventilation flow that allows for adequate hygrometric characteristics.

• The exterior carpentry of the envelope must be of high quality to minimize energy losses that can occur through them.

• A sustainable house design that meets European environmental demands must have a mechanical ventilation system with heat recovery, capable of recovering up to 90% of the energy, ensuring that the indoor air quality is safe for occupants.

• The design of a home with these characteristics must include a modeling system for the energy gains and losses of the home.

Sustainable Rehabilitation: EnerPHit Certificate

If we are aiming for an efficient rehabilitation, we must talk about EnerPHit. It is the equivalent of the Passivhaus standard for existing buildings undergoing rehabilitation. The requirements for obtaining the EnerPHit certificate are less stringent than those for obtaining the Passivhaus certificate.

If you are thinking about making renovations in your home and wish to obtain the certificate, you need to ensure that the following parameters are met:

• The energy demand for heating cannot exceed 16 kWh/m²a and that of cooling cannot exceed 25 kWh/m²a (in the case of the Passivhaus standard, for new constructions, the threshold is 15 kWh/m²a.

• The frequency of overheating (25°C) cannot exceed 10%.

• The thermal transmittances (U) of the structural elements must be as follows:

- The transmittance of opaque elements in contact with the outside air (not including the roof) cannot exceed 0.15 W/m²k.

- In the roof, the thermal transmittance cannot exceed 0.13 W/m²k (in the case of roofs, 0.15 W/m²k).

- In the case of opaque elements in contact with the ground and in unheated basements, f × U ≤ 0.15 W/m²k (where f is the ground reduction factor).

- The transmittance of the windows cannot exceed 0.85 W/m²k.

- If the ventilation of the home is done by controlled mechanical means, the efficiency must be 75% or greater, and the electrical efficiency of the ventilation system cannot exceed 0.45 Wh/m³.

- Regarding the limit value for airtightness, this must be n50 ≤ 1.0 h-1. The target value will be n50 ≤ 0.60 h-1.