What are the benefits of sealing your home and how to do a leak test

From 2021 onwards, the NZEB standard will be mandatory for all newly constructed buildings for which planning permission has been issued after 31 December 2020. This means that all buildings constructed from now on must be near-zero energy buildings (nZEB: near Zero-Energy Building), i.e. very energy efficient. Another requirement is that this very low energy requirement should be met as far as possible from renewable sources. Whereas until now we have all managed our own energy consumption in our own way, now the house must be designed to meet EU requirements and those of the Ministry of Regional Development and Public Administration. It's no longer just about what each of us thinks about energy consumption and paying the bills, but about a Europe-wide requirement to protect resources and reduce the noxiousness of burning fossil fuels. In the new houses we build we will use less energy for heating air, water, cooling, air conditioning, ventilation. How can we do this? By building well-insulated and well-sealed houses so that energy losses are reduced to zero.

What makes a house energy efficient

For a building to be as energy efficient as possible, it must have an airtight envelope. It must be very well insulated, have high performance windows and doors, be oriented so that it benefits from solar gain in winter, and have heat recovery ventilation systems. The Passive House is currently the most energy-efficient building concept and a benchmark in low-energy house construction. Passive houses are built all over the world, but in Romania there are already such houses, some of them with certifications from the Passivhaus Institute in Germany.

Passive house certification is received if certain criteria are met. Measurements are made to determine the energy efficiency of the house, but also to determine the indoor comfort benefits for the inhabitants. One of the requirements is high air tightness. To determine the airtightness of the house, a specific test called leak test or blower-door test (described at length below). According to this test, a passive house must have less than 0.6 shifts/hour. To give you an idea of the difference, Zecaph - a passive house standard energy efficiency designer and consultant - says that now, in Romania, a new construction falls between 5 - 26 air changes per hour.

What are the advantages of a well-sealed house

The main advantage is lower heating and cooling costs. The very good sealing means that there is no uncontrolled air exchange between the inside of the house and the outside. Such an exchange would also mean a loss of heat from the inside to the outside in winter, or an influx of heat from the outside to the inside in summer. The temperature difference between inside and outside makes air move, circulate, and an unsealed house allows exchange with the outside. As a result, indoor thermal comfort will decrease, and additional energy consumption is needed to bring it back to the desired level. This extra consumption will show up in your bills.

Another disadvantage of uncontrolled air exchange between indoors and outdoors is condensation. Uncontrolled air movement also affects the humidity inside. The extra moisture in the air can condense in areas where there is no thermal insulation or it is interrupted because the walls are colder there. Permanent dampness leads to mould growth. There is a misconception that very good sealing leads to condensation. It does not! The foils used for sealing allow water vapour to escape, but not air circulation.

If the tests show that the building is well sealed, then the house will certainly have a high level of sound insulation and you will have the guarantee that the work on site has been well executed and the construction has no hidden defects.

How to seal the house on site

To perfectly seal the building, a foil is used which must be installed continuously on the inside, i.e. on the inside face of all walls, the roof and over the concrete floor slab. Design specialists have a rule - the pencil or red pencil rule - to determine a perfect seal. The rule says that on a section of the house project, you should be able to pencil over the sealant without lifting it off the paper.

For the seal to be perfect, the installation team must pay close attention to all the joints between the sealing foils. The sheets overlap and are taped with special adhesive tape. There are sensitive areas, such as around doors and windows, and balconies that have an external platform, where sealing must be done with great care. Also, installation crews must work carefully to ensure that the penetrations made to fit the pipework do not damage the sealing film.

In order to prove that the fitted film is continuous, with no leakage leading to air leakage, the blower-door test is performed.

Tightness test orblower-door test or theblower door. Why is the blower-door test necessary?

This test checks the airtightness of the building, the quality of the work carried out and identifies any areas with airtightness problems, where air is leaking and then remedies them. Vulnerable areas are those at the joints of envelope components, windows, doors, at penetrations of pipes or electrical routes. The air tightness test is performed to measure the air tightness of a house and answers two questions: "how much air is entering or being lost from the house?" and "where does it go?".

For the test, a blower door incorporating a powerful fan is fitted tightly in the gap or within an exterior door of the house. Sealing is ensured with a flexible foil that seals the door gap where the fan is installed. The fan blows air in or out and thus creates a pressure difference between the inside and outside of 50 Pascals. Measurements made during the test aim to determine the n50 value which shows the number of air changes per hour at a pressure difference of 50 Pa. The value allows the detection of leaks by means of an anemometer (air velocity measuring instrument), smoke machine or thermoscanning. During the test, an auditor can see from outside the house which areas are leaking air. The places where installation faults or leakage problems are found are usually around windows, doors, at the junction between elements of the house (walls/roof) or in areas where cables or plumbing tubes are penetrating the walls. With thermoscanning and smoke generator even the smallest heat losses or temperature differences are located by the blower door test. In addition to these qualitative observations, the blower door also provides a quantitative measurement of a home's air leakage. Based on the data collected, the building's energy losses can be estimated and improvements made.

Ideally, two blower door tests should be carried out during the construction site, one at an intermediate stage of construction and another at the end. The benchmark test, however, is the one at the end, when the construction is finished and the finishing touches are completed. This test is mandatory for passive house certification.