New Build

Ventilation For New Builds

New Build

With the new building Regulations introduced in 2019, a property built today has to have an air tightness of 5m3 / (h.m2) at 50pa or less. It is important as buildings become more airtight that adequate ventilation is maintained because there is very little normal air leakage. You are still allowed to install holes in the wall and intermittent fans as a form of ventilation were the air permeability is greater than 3m3 /(h.m2 ) and lower than 5m3 /(h.m2 ).

The minimum total equivalent area of background ventilators providing general ventilation should be 42,000mm2 with an additional 7,000mm2 for each additional 10 m2 floor area above the first 70m2 of floor area measured. For single storey dwellings an additional 7,000 mm2 per dwelling should be provided. The average wall vent has a free area of 4000mm2 . If you take the floor area of your new home that will come to a lot of wall vents and far more than just one vent per room.

If you do not plan the ventilation of your property and instead just decide to go with wall vents, you then have a problem if the air tightness of the building comes under 3m3 /(h.m2 ) as a mechanical ventilation system is then required. The question is why spend so much money on air tightness products and insulation to allow it escape through uncontrolled ventilation.

We would recommend that you plan from the very beginning to install a ventilation system not only from an efficiency point of view but as a necessity to keep the air in your home healthy and at the correct moisture level. Heat recovery ventilation is probably the best solution and the most energy efficient and we have a range from Elta Fans, but there is other alternative which will deliver the same quality of air but at a far reduced installed cost. Many heat recovery units can quote high efficiency levels of around 90% but are very dependent on the air tightness of your house. What has to be subtracted from the energy savings is electric usage and maintenance cost of the unit. What also must be considered is the end of life replacement cost. The saving with a heat recovery unit against other units listed below are between €100 to €50 per year.

(1) Positive input ventilation (PIV) with constant running extraction fans. This system is very energy efficient and would come close to the savings you would make with a Heat recovery unit. This unit is also suited to houses with stoves fitted.
(2) Centralised mechanical extraction ventilation (MEV) is a very good whole house central extract system, we have a choice of three unit. This system is very low maintenance and cheap to run.
(3) Decentralised mechanical extraction ventilation (dMEV) system operates the same way as a MEV system but is more suited to houses that have not been design for installing ducting. This system can also be installed were ventilation has been left to the last minute or not really planned for in the initial stage.