Recuperation for single-family houses

Recuperation for single-family houses.

Ventilation consists in removing contaminated air from rooms and supplying fresh air in its place. In air, bacteria we breathe, viruses, mites, allergenic factors, molds, short, flower pollen, and their concentration is all the greater, the higher the humidity in the building. The Polish Construction Law precisely defines the amount of air, which should be removed, then replace with fresh:

Operation of mechanical ventilation with heat recovery.

The house loses a significant amount of heat along with the exhaust air discharged to the outside. In a modern and energy-efficient building, this cannot be allowed and the heat should be kept as much as possible. It is possible thanks to the use of an air handling unit with a heat exchanger. Such an exchange is called a recuperator. It enables the recovery of heat from the exhaust air, in order to heat the air taken from outside the building. In single-family houses, recuperators with a cross-flow exchanger are most often used.

Streams of warm air from inside the house and cool from outside flow through partitions made of a material that conducts heat well.. The exchanger is therefore a "sandwich" of warm and cold partitions, but most importantly, fresh and used air streams do not mix with each other.
As the name suggests, in recuperators with a cross-flow exchanger, the streams of supplied and removed air intersect with each other. Such exchangers allow you to recover up to 80% warm. However, if we use a recuperator with a double exchanger, this factor increases to more than 90%.
Tight windows, doors and ventilation ducts (except places, where gas combustion takes place) they cause uninterrupted operation of the recuperation installation, without unnecessary heat loss.

Construction of recuperators.

For a single-family house, a recuperator with dimensions not exceeding is sufficient:
-length - 1m
The recuperator consists of a heat exchanger, two fans forcing the air flow, filters, optional heater (preliminary and / or secondary) and control.
Outside air, before it goes to the ventilation duct system, it is pre-cleaned with a filter, before the heat exchanger, and then heated in the exchanger.
Fans in a good heat recovery unit should be adapted to continuous operation, and their power usually does not exceed 120W. Means, that they do not produce significant and nuisance noise. The place to install a recuperator should, however, be carefully selected so, so that the operation of the fans and the noise of the air carried by them do not disturb the rest. For this reason, it should be kept away from the bedroom. Primary air heaters - installed on the fresh air supply line before the recuperator or secondary – installed on the same pipe but behind the heat exchanger, are optional devices. The heaters installed in it have considerable power - up to 2kW, but they turn on briefly. Some recuperators have a defrosting system. It is based on this, that when the exchanger is frosted, the fan that pushes fresh air is turned off, and the AHU works only with a fan ejecting used air from the building. After defrosting, the fan returns to its operation. The recuperator housing should be made of a sound-absorbing material. Usually, plastics are used for this purpose. The housing itself should also not make noise. Its appearance is also a very important aspect, especially when the recuperator is installed in a visible place. Filters should be cleaned and replaced in accordance with the recommendations of the AHU manufacturer.
The recuperator can be equipped with a mechanical and electrical control, electronic or digital. In units intended for use in single-family houses, it is usually simplified. However, the possibilities resulting from digital or electronic control significantly affect the ease and convenience of the system operation, allowing e.g.. for temporary switching off and on of the air handling unit in daily or weekly cycles or depending on the prevailing weather conditions.
The most important parameter of the recuperator's work is its compression, i.e. the force with which the device ejects used air and sucks in fresh air. With too little pressure, the air may not reach some diffusers. For this reason, recuperation installations should only be designed by specialized companies.
In single-family houses, recuperators with a pressure from 150-300 Well.

Installation of a recuperation system
in a single-family home.

The air from the recuperator is distributed to individual rooms (vertically and horizontally) ventilation pipes. Spiro type metal pipes are best for this purpose, insulated with mineral wool. The insulation protects against sound transmission and heat loss in the sections leading through unheated rooms (attic, basement). It is best to distribute the ventilation system in walls and ceilings, thinking about it already at the stage of building a house. Then it will be easiest to route the cables along the shortest possible route, without unnecessary kinks. If the installation is made in an existing house, it can be hidden above the suspended ceiling. At the exit, in rooms, diffusers are installed (supply and exhaust), which make it possible to regulate the outflow and exhaust of air. By turning their dial you can increase or decrease the air flow rate. Installation of a mechanical ventilation system with heat recovery in a single-family house is an expense of approx 15.000 zloty, which, however, quickly pays off in savings on heating. By accepting, that the heat lost by ventilation in a sealed house is approx 40% all supplied heat, this is what we recover when using a recuperator 70-80% from those 40%, that is, almost 30% total heat lost. Means, that heating bills in our home can become up to 30% lower!


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