How to make a conservatory or sunroom more energy efficient

Operating as simple heat-shunts for the rest of the house on warm winter days, conservatory spaces can be accessed neatly through an existing set of French or single external doors, and separated in terms of security and heat loss from the house by this heftier external door. Space is space — not indicated space, not imagined space, and to have an affordable, extra room, especially a light-drenched slouch spot of somewhere to tease up a few tomatoes by the kitchen door — what’s not to love?

Chris Hodgkinson, managing director of the House Buyer Bureau, recently threw a large rock at the UK's beloved middle-class status symbol. He stated in a blog post for thisismoney.co.uk that the presence of an older conservatory on a spec was a turn-off for buyers, which could reduce a selling price by as much as £15,000 (around €17,500). 

Guiding a business that buys in property for quick, cash deals, Mr Hodgkinson suggests that purchasers want “proper rooms” with proper walls, and proper roofs that are a full part of the house, and that perform just as the rest of the house does in terms of heating and cooling. It would, he said, take another €2,500 to pull the conservatory down and get rid.

This shattering idea seems extreme (a little offensive), and I needed to find out more. We asked an award-winning architect, and a supplier of energy-efficient glazing based in Cork, to throw some light on the subject.

Paul McNally MRIAI is the director of The PassivHaus Architecture Company, Cork, and one of the pioneers in passive house design and detailing here in Ireland. I asked for his reaction to this report from the UK, and his thoughts on standard budget conservatories functioning as sustainable, small extensions.

“I would challenge the estate agent’s premise. In my opinion — and remember I am not an estate agent — I would tell anyone selling a property that the conservatory is not a €15,000 liability. Knocking a conservatory is likely to cost as much as €5000 (depending on its size and complexity). 

"So, if we presume all purchasers do indeed want to knock the conservatory, then the market price is X, and they will factor in the demolition along with all the other changes they will make to the house. Another purchaser might love the extension, and the value to them is X plus €5000.

I would not recommend doing substantial works to a house that you plan to sell, as you will never get the investment back. Yes, superficial works, like a lick of paint, taking up horrible carpets or stripping naff wallpaper are cheap and drastically improve the saleability of any property, but not major moves like demolition or additions."

What about the look and character of the standard PVC conservatory — does it kill the look of a house to have an Edwardian lean-to or roomy Victorian conservatory occupying one side of the house?

Paul responds: “To me, there are two considerations. Aesthetics and comfort. As an architect I need to park my designer’s judgement and say that taste is a very personal thing, there is nothing wrong with a PVC extension on dwarf walls. They add incredibly affordable extra accommodation space to a home and give great enjoyment as they allow you to connect to the outside. Visually they are usually situated in your private garden space so who cares if they are not going to win a design award.

“My only warning is that these spaces are potentially prone to overheating, as they typically have lots of glass and no external shading. Yes, overheating is a real thing in Ireland! Whilst the balance will be just right in spring and autumn, for a narrow time period as soon as the sun comes out properly the space will be unbearably hot. 

"Make sure there are lots of operable windows on multiple sides to get cross-ventilation and even still you will need blinds, because if you are sitting in direct sun, the air cannot shift that heat. Even then, this will still be uncomfortable, and the blinds will block your view. External shading is the only thing that works.”

What about colder months when conservatories can creak in the wind and with low U-values, cannot be heated effectively? Paul offers a word of warning that touches on compliance, not simply feeling snug and smug with a fully glazed addition. 

“In winter, no matter what the sales agent tells you, the heat losses with all that glass will feel uncomfortable. This means if the space is not separated from the main house by insulated doors, you will have substantial heat loss to deal with. Installing heating in a space like this is probably going to be in breach of the building regulations because there is almost no way you can have a space that is to be heated with that much glass and still comply with the Conservation of Fuel and Energy (Part L) constraints.”

BOOST THERMAL STANDING

Paul suggests two approaches to improve the thermal standing of an older conservatory or sunroom: Have it thermally separated from the main house by closing, insulated doors, only use it in summer, and have external shading (overhanging roof or similar structure) to keep the sun off the glass with no heating system and good opening sections—or build a really well-insulated solid roof, and only put the right amount of glazing where it is most effective, and make that triple-glazed high-performance frames. 

Make it airtight. Install proper ventilation, and insulate the hell out of the floor and walls, but here we are back to the expensive extension.

So, if we have a freezing/boiling glorified greenhouse, what about a retrofitted solid roof? Are there ways and means of warming up the conservatory you already have that goes beyond the common solution of thermal blinds? Absolutely. These insulating products are bespoke, and fast to install, but they do come at a considerable spend that has to be regarded as a long-term investment in comfort and efficiency.

Robert Kennedy explains the Guardian Roof System, offered by his team at Sky Windows, Cork (skywindows.ie), an innovative answer to a cold-glazed roof leaking energy in and out year-round: “The Guardian roof is a suitable replacement for most shapes of conservatories, those with roofs glazed with glass or roofed in poly-carbonate. The roof is engineered to be self-supporting, so there’s no need for a steel portal frame. 

"It’s versatile, as it can also be used when constructing a new sunroom/extension. Fully installed, the system offers a maximum U-value of 0.145W/m2K, enabling a conservatory to be used as an extra living space all year round, as it can be cool in the summer and warm in winter. A typical job would be a size of around 3.5 metres x 3.5 metres and would start at around €10,000 (including VAT) but prices are variable depending on the job and the client's requirements.”

Robert agrees with Paul that a conservatory or sunroom must perform in terms of energy efficiency to be truly liveable and to act like a real extension. “When building a new sunroom or replacing the roof in an older one,” Robert advises, “avoid a glazed roof, particularly in a southerly aspect. 

"The roof should be insulated to as high a standard as possible and include a roof window for additional light and to provide ventilation on warm days. The windows could be double or triple-glazed depending on budget and the site orientation. It's also possible to replace the glazing in older conservatories with newer A-rated glazing to give greater insulation in the colder times.”

Anything else Robert would suggest keeping our older conservatory in good order? Robert adds: “Handles, hinges, locks and other moving parts in a conservatory require maintenance. This can be done DIY by having a six-month regime of lubricating all these moving parts with a good silicone-based lubricant spray. Older PVC conservatories can look a bit tired and jaded after a few years. The colour of the frames can be revived by using a PVC Cream cleaner which can be got from most good DIY stores.”