When we talk of sunrooms this is quite a broad term and could range from the original glass conservatories right to the modern-day lounge so let’s have a look at each and see how they developed, how they were built, and how they perform.

When I was a child (in the 1980s) we lived in a park in Midleton called Suncourt. If you have ever lived in an estate like this you will know that when one person gets something new added to their house, it catches on like wildfire and every second house wants one. It might have been a porch, PVC fascia and soffit, or indeed the HTV aerial. The smallest upgrade caused a stir though the venetian blinds and next thing you knew another van was pulling up outside your neighbour’s house.

In those days, what we now know as living spaces were really a collection of rooms, principally the kitchen, the dining area, a separate sitting room, and probably a ‘good room’ out the front with no open plan flow and indeed no connection to the garden save for the back door from the utility room. This meant there was a huge gap in the market for an additional room that would add leisure space out the back.

A basic conservatory

The first iteration here was the humble conservatory. This was a glass-roofed and glass-walled extension built on a concrete slab, connected to the house. It was a huge improvement and the first room built for conversation and enjoying the view of the garden, rather than watching TV or eating Christmas dinner.

Though the layout was reasonable, it was laden with fault in terms of building technology, The concrete slab often had no insulation and because it was a single slab, had no real attention to damp proofing or guarding against cold bridging from the outside so it was susceptible to damp and condensation. The walls and roof were glass and in some cases single-glazed so it was really more of a high-end green house. There was no protection from the relative extremes of the Irish climate so it was roasting in summer and baltic in winter... suffering literally with ‘the green house effect’.

A sun room

The next improvement, and what I believe you are referring to is the slate- or tile-roofed sun room.

This was a big improvement on the conservatory above because it had a solid roof so you had an opportunity to insulate the roof void.

Insulation keeps a level of heat in the room in winter and protects the room from the extremes of heat from the sun in summer. Typically in this design you have less glass on the walls and more masonry below so you have a more forgiving and robust design items of insulation and damp-proofing and this approach tends to carry through to the floor too. In fact, glazing that runs though to the floor is a very complex detail to get right which often causes problems even today.

This more advanced iteration was certainly much more expensive to build and took a lot longer but with a far superior product. Now you had enough wall space to add a radiator so it tended to perform similarly to the rest of the house in most respects. However, you need to be careful to get your roof insulation detailing correct in terms of the type of insulation used and the ventilation requirements.

A modern lounge

Given that you are designing a new home on a blank canvas, I would urge you to design a modern lounge. This is a room that will be connected to your kitchen/dining area and may have the option to be closed off with a sliding door of some sort. (There is an ongoing debate as to the level of open-plan connection that works best here so this can be a personal decision and best to have options down the line).

The new lounge may be contained in the body of your house or it may be a single-storey annex. Either way it will be designed to perform similarly to the rest of the house and to all correct stringent building regulations. This is a wonderful family space and well worth the investment. It will cost a good bit more than the traditional sunroom, but in reality, they are worlds apart

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• Kieran McCarthy is a building engineer, and director of KMC Homes, who specialise in designing and building luxury homes in Cork. He also presents the RTÉ TV show ‘Heat My Home’, showcasing deep retrofits in Irish homes; kmchomes.ie
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