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Creating a healthier, fresher and more comfortable home…
In simple terms MVHR removes stale moist air from the house and replaces it with fresh filtered air from outside, by means of a heat exchanger within the unit it can pre-heat the incoming air on demand. The MVHR unit replaces traditional means of ventilation, being far more energy efficient, healthier and cleaner as well as being controllable it renders passive stacks and trickle vents obsolete.
With ever increasing fuel prices as well as environmental concerns reducing energy consumption has become a priority, to this end building regulations are progressively changing as are building methods and materials.
Great advances have been made in reducing heat loss through the thermal envelope by improvements in insulation. As a result of this, heat loss through air leakage is a much larger percentage of the overall heat loss. In order to reduce heat loss through air leakage new houses must be constructed to high standards which include the use of Accredited Construction Details (ACD,s), Enhanced Construction Details (ECD’s) or similar recognized construction details. There is of course a downside to preventing air leakage in a property. The occupants need fresh air and the property needs to be kept free of excessive moisture. People need less than 1litre per second of fresh air to breath properly but in order to remove volatile organic compounds (VOC’s) and excessive moisture, the air in a house needs to be changed about once every two hours. Building Regulations Part F gives guidance on the level of ventilation required for each dwelling, based on size and occupancy.
Too airtight a house for thermal efficiency and there is not sufficient air for the well being of the occupants and the dwelling. The solution to this dilemma is mechanical ventilation with heat recovery.
Very simply, an MVHR unit has two fans and a heat exchanger (which works in a similar way to a car radiator). One fan extracts stale air from the dwelling whilst the other pulls in fresh air from outdoors. The incoming air is filtered before being passed over the heat exchanger; the heat exchanger enables the incoming fresh air to pick up the heat from the outgoing stale air without actually coming into contact. In warm weather when it isn’t desirable to pre-heat the incoming air a by-pass valve is usually fitted to divert the incoming air around the heat exchanger. Thereby the system exhausts the warm extracted air outdoors whilst replacing it with fresh filtered air with no heat exchange occurring.
In order to ensure that the fresh air is properly distributed throughout the house and that the stale air is removed from where it is generated, a series of concealed ducts or pipes are run from every room to the MVHR unit. Stale air is taken from the ‘wet’ rooms (bathrooms, kitchen, utility room and WC’s) and fresh air is fed to the living rooms (lounge, dining room, bedrooms etc).
It is most important that the MVHR system is considered and designed into the house at a very early stage and is accounted for when planning plumbing and other services. The MVHR unit would normally be housed in a loft space or a service cupboard but there is no restriction on where it can be located. The more central it is the better, as this allows for shorter ducting runs resulting in greater efficiency. A good MVHR unit can be up to 95% efficient which means that if the indoor air temperature is kept at 20°C and the outside air temperature is 0°C the incoming fresh air will be pre-heated to 19°: a huge saving in both heat retention and your energy bills.
A well designed MVHR System will make a positive impact to SAPcalculations.
The systems are commissioned to supply the required minimum whole house ventilation rate 24 hours a day, 7 days a week, higher levels of ventilation being available on demand via various means of switching, sensors or programming.
In order for us to provide you with an accurate quotation and our considered recommendations, we will require the following information; A set of drawings, floor plans with elevations if possible, plus any special requirements you would like us to allow for. Following this, trusting our price is favourable, we will start to commence CAD (Computer Aided Design) Layout Drawings. In this process our project manager will liaise with your architect / site representative or Project coordinator to ensure the systems design is correctly incorporated into the buildings structure, without conflict of other services whilst serving the clients requirements.
Once the layout of the system has been agreed, we will deliver materials to site and commence 1st fix, this phase in new builds usually takes place as soon as the building is water tight, by this we mean when the roof is on felt and battened. It is preferable for the MVHR system to be installed prior to 1st fix Electrics & Plumbing, as it will be the largest of services being installed.
Once the ceilings have been plastered & painted, the electrics to the building are in and power is available and internal doors have been fitted it is time for 2nd fix & commissioning.
Our designated project manager will be on hand throughout the project to give guidance and assistance where required, ensuring a swift and untroubled completion.
We offer a wide choice from a range of manufactures enabling us to specify the best system to meet your requirements and your budget. All Systems we provide are Appendix Q approved. Where ever possible we use (and recommend) Lindabs’ Safe Seal Ducting systems. Please view our info centre to see a selection of our recommended units.
