Air Conditioning

I can see circumstances where air conditioning would be necessary in poorly designed new houses. i.e huge south and west facing windows. Clearly the designers are not carrying out an overheating analysis at design stage.

An air-to-air heat exchanger can provide cooling in the summer and heating in the winter.

If it is a large open-plan area then the "cassette" in the ceiling might be a good way of doing it?

(Installation not cheap as requires an f-gas certified installer)

Dont live with it, but do work with it. There's not too many domestic installations here, and many of those are in the trade. Having said that, any I know are happy with it. Its not cheap, you'll pay €2-3k per room

I agree that it's a generalised comment but I also think that the negative impact of solar gain is often overlooked in newer builds. Cheap glazing has a lot to do with it as the glass used often has a higher g-value which allows more heat to pass through. I recently put in a large west-facing slider into my own kitchen/dining but I was careful to specify glass with a low g-value. As a result, the solar gain from the glazing is negligible - to the extent that we haven't even bothered with blinds. In contrast, the bedrooms on the same side of the house with older double glazing (installed by previous owner) bake in weather like this - even with blinds.

OPs situation is tricky. I have friends in similar positions in refurbished houses. MVHR is the system of choice at the moment and they're great for managing humidity. However I think it's only a matter of time before ventilation systems with air conditioning become the norm. I was talking to a specifier of MVHR systems who was looking at the idea of putting a cooling element into the intake duct that could be linked back to a heat pump to provide cooler air into a dwelling. Similar systems run heat pumps in reverse to cool floor slabs via underfloor heating pipework. You just have to be careful that you don't introduce condensation in such circumstances. With anything, it's about getting a balance.

Generally, extremely large windows, even southern ones. Cause the loss of more heat than they gain. In Ireland, overheating is simply not likely. Situations where I have seen overheating, would be from super insulated and airtight fabric, that retains close to 100% of energy. In this can minor gains accumulate. But it's easily solved by opening windows to create air flow.

Ireland simply isn't warm enough for over heating to be a major issue.

Sure, it only has to happen a few weeks a year to cause a lot of discomfort. There are defin Irish homes that overheat too much to be cooled by night opening of windows. I am not saying they need air conditioning but opening the windows at night isnt always enough. Large southern windows are defin risky in some designs.

what brand/model did you get if you don't mind me asking?

looks interesting thanks

My 1930's build solid brick house over heats in the winter summer massively. The rear is south facing and we have had over 40* heat measured in the rooms over the last few summers.

We are about to start renovation (the house is as is, single glazed, no insulation etc) and an over-heating study is a significant part of the final design. (a mixture of low-g glass, external louvres and electric awnings)

Yeah sorry, I meant summer!

My point was that if an old house like mine over heats a modern house with better insulation and air tightness could/would certainly over heat without taking measures (based on an over-heating survey) to avoid.

Why is your uninsulated house indicative of how an insulated house performs? I think perhaps you are misunderstanding or forgetting how insulation perform in hot weather. When it's warm outside, insulation slows the entry of heat.

Airtightness is pretty easy to nullify. Open a window. Which you are only supposed to do when the inside is warmer than the outside. Natural ventilation strategies like that work in much warmer climates than Ireland

There's a few key points that are incorrect there.

That is incorrect. There are u-value requirements to meeting Irish building regs, including u-values of glazing, and increase U-Value means a lower SHGC. Therefore meeting those U-values means you will reduce the heat gain via windows via two means. The conductivity, and radiation (solar gain is radiation). That applies to all modern windows regardless of whether a specific overheating study is undertaken.

You single glazed windows wouldn't have nearly the same protection. So it's does not imply that a house with better insulation would certainly overheat more. Which is the claim I'm refuting.

I literally state in that paragraph that it can happen in super-insulated house, when near all heat is retained (as any gain accumulate). It's a real consideration for passive house design, as anyone who has studied passive house design figured out early. You are using extreme examples at either end, nobody mentioned 1930s house that don't meet building regs. Nor did anybody mention passive houses.

The claim was that overheating is a problem with the majority of new houses now. That claim is not true imo. Pointing out that it happens at extremes cases of A and B does not mean it happens for every type between A and B - FWIW those two extremes overheat for opposite reasons.

If the inside is 40* due to massive solar gain and the outside is 20* then opening a windows will be huge. That's literally how natural ventilation works. It works in much warmer climates than Ireland. (My office is an uninsulated 1900s brick building that used natural ventilation very success at part of mixed mode)