Foreword

The following statement on this webpage represent the personal opinion of the owner of prodomo Ireland.

As there is no dependence on any sales of ventilation systems, an attempt is made to treat the whole subject as critical but objectively as possible.

prodomo Ireland is no longer engaged in the sale of ventilation equipment as of January 2022.

Consequently, no more quotations and supplies will be made in this regard.

If required, independent consultation on suitable ventilation strategies and installation details can be provided.

However, please do not expect this service to be provided free of charge.

1. Natural Ventilation

Natural ventilation is mostly an accidental product, where air exchange is supposed to take place through intentional or unintentional openings in the building envelope. Intentional openings are windows with an opening mechanism, the famous hole in the wall, which is often referred to as a background vent (which of course sounds much better) or the infamous trickle vent in the window frame.

Unintentional openings are cracks, gaps or joints in the building envelope through which air can enter or escape into the building. Such openings cannot be regulated at all, the former only very moderately.

The general problem with natural ventilation is that there is either too much air exchange or almost none at all.

On a cold and windy day you can clearly feel the draught, while on some windless days you still haven't achieved a noticeable exchange of air through natural ventilation even after hours. Hence the chosen designation of accidental ventilation.

2. Mechanical Ventilation

With mechanical ventilation, the air exchange is effected by a fan and can thus be adapted to the corresponding demand. There are different variants, the most common of which are explained in more detail in the next paragraph.

In contrast to the current Building Regulations for ventilation (Part F - 2019), the PIV (Positive Input Ventilation) variant is not considered any further.

However, if you are desperate to have polluted air (dust and insulation fibres) blown into your house from your attic, please contact the clever guy who made the system socially acceptable here in Ireland.

Background ventilation???

Please go back to the section "How can it be achieved" and read (again) the execution regarding natural ventilation.

Background ventilation is not an option for energy efficient houses!

Mechanical Extract Ventilation (mEV) ??

The simplest variant of mechanical ventilation. In most cases, these are single extract fans that extract stale air from bathrooms, kitchens or utility rooms. The supply of fresh air is subject to the random principle.

Cooker hood extractors work according to the same principle, but are not included in the definition, as these extractors only remove the special kitchen steam from cooking/baking/frying.

Demand Control Ventilation (DCV) ??

Is nothing other than the refinement of the mechanical extract ventilation.

Simply add "controllable" vents for fresh air supply and voila [French; “there you have it“] - the demand controlled ventilation system is born.

Such a system does probably supply an acceptable performance in Mediterranean weather conditions. Here in Ireland it can easily create discomfort in the winter as you get „fresh air“ with current external temperatures blown right into your home.

More and more users do not find this „feature“ magnifique [French; „magnificent“] and the frustration about noticeable cold air infiltration outweighs the happiness about the saved commissioning for a DCV.

Nerds could probably solve the problem by adding an earth heat exchanger, which pre-heats (or cools in the summer) the incoming fresh air through geothermal energy. But such an AddOn requires knowledge and could drive the initial investment beyond heat recovery ventilation level.

Naives do might consider the use of air supply vents with integrated heating elements, as seen quite often on online selling platforms here in Ireland. Beside unshakeable belief in the overcome of basic physical laws, this strategy requires a noticeable amount of extra money for at least 6 months per year to power the electric heating elements.

Mechanical Heat Recovery Ventilation (mHRV) ?

The supreme discipline in domestic ventilation.

Since the cross-flow heat exchanger for domestic ventilation systems was invented by another German, this ventilation system has been dominant.

The actual working principle is as simple as it is ingenious: one fan each conveys fresh air into the house and stale air out of the house.

The two air streams do not meet directly, but the heat exchanger uses the heat of the discharged air to preheat the fresh air.

This means that no uncomfortably cold air is blown into the house in winter, which first has to be warmed up by additional heating energy.

A major challenge with mHRV is the ducting required to transport the air into or out of the individual rooms. However, good planning and the selection of suitable components make even this challenge solvable.

mHRV systems are available in different versions. Central mHRV systems (ventilation unit and ducting) are certainly familiar to most people. However, there are also decentralised ventilation units available, operating with heat recovery. In some of such decentralised systems, smaller cross-flow heat exchangers are used, while the compact devices for wall installation are usually equipped with heat accumulators.

In general, central ventilation systems are suitable for all house sizes, while decentralised ventilation systems only work (economically) for ventilating smaller units, such as apartments or houses up to approx. 150m² total floor area.

Since we human beings breathe constantly and need fresh air to do so (by generating used air as well), the mHRV must operate 24/7.

Many customers still think that such a mHRV system should only be operated intermittently and can be switched off at night because we are usually asleep anyway ...

Unfortunately, the current Irish building regulations are very generic in terms of ventilation and minimum supply rates for fresh air.

In Part F-2019, the minimum rate calculations are carried out by using either the number of occupants or the overall floor size of the house as the basis for calculation. Either way, the larger value of these two calculation options must be used. More living space does not automatically lead to a higher demand of fresh air, as space does not consume air.

Other countries are much more advanced in terms of ventilation concepts.

The German DIN Standard, for example, specifies four different ventilation levels for healthy indoor air:

    1. moisture protection

    2. reduced ventilation

    3. nominal ventilation

    4. intensive ventilation

 
As a rule of thumb for mHRV, a simple calculation can be carried out, according to which 30m³ of fresh air should be allowed for each permanent occupant.

Furthermore, the ventilation system should be designed in such a way that the capacity of the system can be increased by at least 50% (boost mode) when required.

Without question - the respective ventilation strategy always depends on the energy efficiency of the building.

Installing a mechanical ventilation system with heat recovery in an uninsulated & draughty house with single-glazed windows will not improve living comfort. On the other hand, natural ventilation does not work in a house built according to today's standards for thermal insulation.

"Build tight (and well insulated), ventilate right" is the mantra for contemporary building design, in which energy efficiency is compatible with living comfort.

 Unfortunately, the "one and only"  ventilation strategy that can be applied to all houses does not exist.

Various parameters such as house size, number of occupants, user behaviour, etc. differ for each house and therefore an individually adapted ventilation strategy must be worked out.

„There are no problems, only challenges.“ should be the guidance when creating your ventilation strategy.

Proper installation, the expected performance and easy maintenance are the key facts for you as the user.

Not every installation attempt will meet these requirements in the long term.

Especially in winter, I am often approached by homeowners regarding the prevention of mould.

However, it is important to know that in addition to the appropriate ventilation strategy, the surface temperature of critical building components such as exterior walls and window reveals is also important in order to prevent mould.

If this temperature is in the critical range (too cold) due to thermal bridges, the best ventilation system may not help me eliminate my mould problem.

Experience is simply the name we give our mistakes.

Oscar Wilde

Unfortunately, there are a large number of mistakes that can be made both during the installation and during the use and maintenance of ventilation systems.

The following examples do not claim to be exhaustive.