Be aware of your retrofit obligations –

Be aware of your retrofit obligations –

Leading energy consultancy has advised homeowners considering renovation projects to be aware of their potential obligations under Part L of the building regulations. The regulations set mandatory energy performance targets for dwellings undergoing “major renovation”.

This article was originally published in issue 37 of Passive House Plus magazine. Want immediate access to all back issues and exclusive extra content? Click here to subscribe for as little as €10, or click here to receive the next issue free of charge

“With the huge demand for housing in Ireland and the uneven rate of new builds coming to the market in comparison to demand, we at have found more homeowners are staying put in their current homes and looking to extend and futureproof their dwellings,” said Daniel Fennell of “The same can be said for first time buyers, who are purchasing existing dwellings that they plan on renovating.”

Technical Guidance Document L 2019 states that dwellings undergoing a major renovation must achieve a maximum primary energy demand of 125 kWh/m2/yr (a B2 rating) or else be improved to a “cost optimal level”, which includes minimum energy performance targets for different building elements.

The major renovation clause is only triggered when 25 per cent of the surface of the building envelope undergoes renovation. “This means that realistically the homeowner would have to be looking at extensive works in order to trigger this clause in the building regulations and won’t unknowingly do it by undergoing small changes to the dwelling fabric, such as changing a front door alone,” Fennell said.

He continued: “The cost optimal clause sets out requirements that need to be achieved when it is not possible to achieve a B2 rating. This would usually relate more to dwellings that have electric heating and would require a new heating system to be installed, which is not always feasible. Another example is old dwellings that realistically can’t undergo works to get to a B2 without huge financial costs to the homeowner.

“At, we specialise in working with the homeowners and their design team to advise whether they are triggering the major renovations clause, and if so, what the best way of improving the energy performance of the building is in order to meet the regulations. We take every dwelling on a case-by-case basis as there isn’t one exact solution in order to meet the requirements.

“By having involved from the initial design stage of a project we can calculate the level of works needed, and we usually find we can reduce the overall cost of the project by providing this advice to the client. This advice extends to areas such as building fabric, ventilation, airtightness, and space and water heating.”