1. Five parts and their roles
They form a whole, and the last holds the result of the other four together. Without it part of the saving is lost.
| Part | Role |
|---|---|
| Reconstruction and insulation of the facade | the largest area of loss |
| Insulation of the roof | the natural exit route for heat |
| Replacement of windows and external doors | affects both loss and airtightness |
| Reconstruction of the heating system | determines how efficiently the demand is met |
| Renewal of ventilation with heat recovery | without it a tight building becomes unhealthy |
According to professional sources, the eligible activity in reconstructing a facade also covers the design, manufacture and installation of elements made in advance in a factory, together with the associated works. The precise list of eligible activities must be taken from the regulation in force, since it has been refined over time.
2. Why ventilation is decisive
Three reasons are technical rather than financial, and the third is a question of reputation for the association. It concerns the indoor climate.
In an insulated and sealed building natural ventilation does not work as it did before. Without heat recovery, part of the saving achieved is lost through air exchange. And a poor indoor climate shows up at once and is associated with the renovation rather than with its shortcoming.
A renovation after which people complain of damp or stuffiness makes the next decision harder. Ventilation is invisible work whose effect is greater than that of the visible works, and this must be explained to residents beforehand rather than afterwards.
3. What is measured at the end of the works
Here is a requirement nobody expects in advance, and it changes the design. It concerns the interaction between works.
| Protocol | Content |
|---|---|
| Measurement of ventilation air flow rates | for each measuring point the designed and measured air flow rate and the difference as a percentage |
| Measurement of building services noise | covering, among others, the apartments nearest the heating substation and the ventilation unit |
The result is therefore verified not only by calculation but by measurement on site. The practical consequence for design cuts two ways: ventilation must be designed so that the measured result matches the designed one, and noise must be allowed for in the positioning of the equipment. The precise list of requirements must be taken from the regulation in force, since it has been refined between rounds.
4. What is often left out
Four things are not at the core of the package but affect the result, and the fourth is the most frequent source of complaint. It concerns later maintenance.
The treatment of balconies and loggias, which are a thermal bridge and a structural problem at once. Insulation of the basement and the ground-floor slab. Stairwell doors and windows, which are in common use and therefore ownerless. And the balancing of the building services after the works are finished.
A new system that has not been balanced leaves one apartment too hot and another too cold. Balancing must be written into the contract, because it is separate work rather than an automatic part of the installation.
Summary and four practical rules
A full package consists of five parts, of which ventilation with heat recovery holds the result of the other four together, since natural ventilation does not work as before in an insulated and sealed building. The result is not verified by calculation alone: the required documents include a protocol measuring air flow rates with the difference between designed and measured values, and a protocol measuring building services noise. Four things are often left out of the package, and an unbalanced system leaves one apartment too hot and another too cold.
Four rules: treat the package as a whole, since a single measure does not reach the class. Design the ventilation to the measured result, not only to the calculated one. Allow for noise in the positioning of the equipment. Write balancing into the contract, since it does not come with the installation.
This article offers professional orientation as at the date of verification. It does not replace the support regulation.