Renovation of ventilation in connection with a pipe renovation in an apartment block
When it is time for a pipe renovation, the bathroom or kitchen are often renovated at the same time. However, ventilation is often forgotten.
When it is time for a pipe renovation, the bathroom or kitchen are often renovated at the same time to improve the comfort of living. However, the ventilation is often forgotten in this context. If the original ventilation system is left in place, it will not meet the modern requirements for comfortable living and energy-efficiency.
A mechanical supply/extract air system improves the comfort of living
In the 1960s, mechanical extract ventilation systems became a growing trend in apartment blocks. A roof ventilator was installed on the roof of the house, either one for the house or one for each staircase, removing air from the wet rooms and kitchen. This satisfied the most important role of ventilation: removing humidity and impurities from the home.
When air is removed from a building, replacement air is needed. This is the Achilles heel of extract ventilation systems, as the replacement air usually comes from window chinks, the staircase, leakages in the structures or, at best, partly from replacement air valves. Replacement air comes in just as it is outdoors: always unfiltered and cold in winter, causing a sense of a draught. The windows often get the blame, although it is the roof fan that actually causes the problem. In winter, the “chimney effect” further aggravates the problem in high houses. When the weather becomes colder, the replacement air flow from outdoors decreases on the upper floors and increases on the lower floors, leading to an increased sense of a draught.
Therefore, good ventilation considerably increases the comfort of living. Controlled supply/extract ventilation means that the supply air comes in through a ventilation unit equipped with heat recovery, filtered and heated in winter. New efficient heat recovery units can heat the supply air to an adequate temperature almost all year round by using the free energy from extract air, and there is very little need for additional heating of the supply air.
Careful planning keeps costs under control
The decree on renovation that came into force in 2013 in Finland requires that when the structures of a house – such as the external envelope or the roof – are repaired subject to a permit, the thermal insulation of the part in question must be improved. There is, however, the option of compensating this with a repair which does not fall in the sphere of the permission but reduces energy consumption. For example, implementing a heat recovery system or improving it in connection with a pipe renovation can help to reduce the requirements for additional insulation and, thereby, also costs. An improvement of energy efficiency during previous repairs can also be taken into account later in other repair work.
Energy savings must never be implemented at the cost of the indoor air quality. The renovation decree requires that when windows of a building are being replaced or its insulation or air tightness improved, the proper functioning of the ventilation must also be ensured. Mounting new and tighter windows may reduce the ventilation and create dewpoints in the cold bridges of the external wall. When a new window stops sweating, humidity condenses on the surface that is the next coldest, usually in the outer corner. This location will be a breeding ground for mould.
Installing an apartment-specific heat recovery system is usually quick and inexpensive, but the costs of the related work may be surprisingly high if the work is not thoroughly planned in advance. If the ventilation is renovated at the same time as the bathroom or pipes, the same enclosures can be used and the structures only need to be dismantled once, without any additional costs. In order to estimate the costs in advance, it is important to examine whether parts of the old ventilation system or its ducts can be used.
Example
Importance of heat recovery in an apartment in an apartment block (Vallox 096 MV, 37/35 l/s, Central Finland).
Amount of energy needed to heat replacement air without heat recovery: 6,598 kWh/year
Energy saved through heat recovery: 4,922 kWh/year
Total annual efficiency of ventilation: 74.6%
Download a calculator for calculating the energy consumption of your ventilation unit.
