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Dormer Bungalow Reinvented as Super-Insulated Ecohome; The Beauty of This External Insulation is More Than Skin Deep!

Like many rural homes, this comfortable dormer bungalow in the beautiful Meath countryside had two major shortcomings: very poor insulation and airtightness, and a tired external appearance. Having already renovated the interior to a high standard, our clients’ brief was to create an external shell of insulation to form a super- insulated and airtight home. This substantial body of work would affect every part of the house, giving our clients a new opportunity for design.  

“Inside- Out” or “Outside- In”

As architects, we usually design from the “inside out”, meaning our buildings are generated from detailed layouts which serve the clients’ brief. Such design concepts make the clients’ physical needs the central organising force which drives all decisions, and provides a lot of flexibility to the architect in how spaces and masses are composed. This project was an unusual experience for us because the interior was complete and the clients were already very happy with how it worked and felt.

For the first time, we designed from “the outside in” to make the best possible external appearance, while retaining window locations, all aspects of the interior architecture and the overall size and proportions of the external walls.

Project Scope

This project required quite an extensive design and procurement process, including a planning application, full technical design, careful budgeting and limited building control submissions. It is a large renovation project including a 28m2 extension, and the removal of the roof covering. 

Energy Efficiency

The house already had a modern heating system but the clients always struggled to keep the house warm in winter. We investigated the wall and roof construction and discovered some incredibly common problems with the fundamental fabric of the building:

  1. Retrofitted roof insulation had been installed with big gaps, allowing cold air to bypass the insulation.
  2. Uninsulated areas remained in the roof which were not insulated at all in the retrofit process.
  3. Poor seals in attic hatches and around openings allowed outside air directly into the living spaces.
  4. Oversized space vents in rooms created an excessive load on the heating system.

This house had a powerful oil fired heating system, the output of which was cancelled out by a continuous stream of cold outside air coming from numerous cracks, gaps and voids in the roof construction. This problem is one of thoroughgoing build- quality dating from the original construction through subsequent attempts to insulate.

Systemic Problem in Irish Construction

Obviously, architects and their consultants design the thermal performance of every building very carefully, and there are now extensive regulations governing all aspects of insulation and energy efficiency. We have a range of tools to design the thermal envelopes of buildings from: manual calculations and simple spreadsheets, to energy modelling software and extensions of the Building Information Modelling Process. Designers currently find it much easier to design a correct specification for thermal efficiency than to actually build an structure which performs according to that design. 

The 1990 building regulations created a new requirement for thermal insulation, but sadly many builders don’t seem to have grasped what insulation did, how it was supposed to work or how it should have been installed. When we open up older cavity walls and roofs during renovation projects, we find that a shocking proportion of insulation from the 1990’s and 2000’s is installed so badly that it has literally zero impact on the energy usage of the building.

Unless insulation is properly installed, it might as well not be there.    

Build Quality is Paramount

Clients are often focused on the quantity and quality of insulation in their homes, but works to improve thermal efficiency are incredibly susceptible to defects in build quality. One gap or crack in a concealed layer of construction can effectively by-pass several thousand Euro worth of new insulation. The most important part of installing insulation, windows or external doors, is proper installation by someone who grasps the fundamental principles of energy efficiency.

This should be inspected by a qualified person very carefully.  

  • There should be no gaps or cracks in or between insulated boards or panels
  • Layers that should be separated should be separate, not “thermally bridged”
  • Layers that should be joined or continuous, should be properly formed and sealed.
  • Always choose insulation methods and products with as few joints as possible to mitigate the impact of careless or unqualified installers.
  • Recommend an air-tightness test as part of the snag inspection; this will identify excessive air- loss in a quantifiable way.
  • If possible, specify a level of air- tightness as a condition of the building contract.
  • Other than this, the only other quantifiable way to check the effectiveness of an installation is to watch the fuel consumption of the boiler (or other heat source) after the building is finished. This is obviously not a sensible approach.  


We designed a comprehensive scheme to reconstruct the thermal envelope of the structure without altering the interior or the main structure:

  • Encase the external walls in a continuous shell of insulation and new render. This will insulate and create a complete airtight barrier.
  • Remove the roof covering and properly install new roof insulation which can be checked for air- tightness before covering up.
  • Rationalise the space ventilation.
  • Replace external doors and windows, which can be fully sealed to the new insulated external shell.  

We look forward to realising this project over the coming months. 

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