Green / Eco-Friendly

Shutters for better home thermal efficiency?

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Shutters for better home thermal efficiency?

I sent quite a bit of time travelling in France and wherever it was an option, staying in older buildings (i.e., pretty much older than century or two) where possible. One thing that struck me was the common use of shutters for doors and windows, not just for security but I presume as an insulation barrier.

Shutters would benefit during the heating season in at least two ways 1) stop most long-wave heat going out and 2) create an air insulation layer of some sort. During the cooling season, it will at least keep radiated heat out.

I guess the trouble is the cost, as well as the massive expanse (number, width) of windows in some houses. There's really no place in my current house to use shutters except in a handful of room. Windows generally have to be inswing too.

There was one Italian household near where I used to live that had the roll-up external shutters (another country where shutters are popular). Not sure if this was used for security, privacy or for insulation purposes.

Curtains and cellular blinds are said to be an option but humidity in my parts means lots of window wiping every day (yes, even in the 0.19 u-factor coated triple-glazed doors I just had installed).
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Oct 9, 2010
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Are you speaking of external shutters on the outside of your windows? If so, they have an enormous impact on my rental house in the summer (built ~1890); basically stops light from hitting the floor and turning the place into an oven. Excluding that, I don't believe they offer any form of "insulation", though mine have reasonably large gaps (1/8"-ish), and don't fit tightly at all.

There's a lot of control variances here, but we fixed the shutters, and the electricity costs during July-August were reduced by 1/3. The summer was roughly the same temp, and the tenant was the same, but we requested she close the shutters to help keep the place cooler, and she said it was dramatic.
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[OP]
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External shutters indeed.

They'll keep the house cool in summer by keeping radiated heat (i.e. solar energy) from getting indoors (even if it's just between window and curtain).

I think even in the cold season having and using them helps:

1) Reduce radiated heat loss (would help even more if the inside of the shutters had a reflective layer)

2) Reduce convection heat loss by reducing air volume against glass and frame even if the shutters do not shut tight. Louvered ones may be less effective though. The insulatie value of boundary air layers should not be minimized.

One added bonus. Shutters would probably reduce window condensation inside the house.
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Feb 9, 2006
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It's actually kind of funny when 100+ years ago people did without AC/ Force Air heat they had what we are now calling innovative ways of regulating the temperature in the house, it's funny every time i hear it as innovative when it was used for 100 years but people stopped because central HVAC got affordable and those techniques fell out of fashion.

Examples:
- Large Overhangs
- Awnings
- Exterior/Interior Shutters
- Multiple Curtains (thick and sheer)
- Non-black roofs
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tebore wrote: It's actually kind of funny when 100+ years ago people did without AC/ Force Air heat they had what we are now calling innovative ways of regulating the temperature in the house, it's funny every time i hear it as innovative when it was used for 100 years but people stopped because central HVAC got affordable and those techniques fell out of fashion.
Spoilt by cheap energy but also custom and tradition? Some places didn't have the luxury thus kept shutters,. It seems most residential buildings built in the past 1/2 century in France and Italy were built with shutters, unless they were designed too modern to have them (e.g., huge glass windows and doors) The U.K. seems to be one place where shutters were either never used or were never in fashion (or they've been removed in the past half century or longer). That may have carried over to Canada. You certainly don't see shutters in Vancouver, even in original period houses that have not had them removed.
Examples:
- Large Overhangs
- Awnings
- Exterior/Interior Shutters
- Multiple Curtains (thick and sheer)
- Non-black roofs
House orientation too. Length of houses in rural areas/farms are built E-W for maximum sun exposure instead of alignment to the road. You seem to find these in the oldest settlements in Québec.

Deciduous trees south of the house.

It'd be nice if roofs were thermochromatic.
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On this very interesting topic, are there ways to get stylish looking external shutters? Not sure how these would work with the house.

Would they be manually operated? Automatic?

Does anyone know if dark colors on your eg. metal roof (with today's level of insulation) cause the house to heat up and thus use more AC?
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aokec wrote: Does anyone know if dark colors on your eg. metal roof (with today's level of insulation) cause the house to heat up and thus use more AC?
Use more? Probably. But I doubt it would be significant enough to matter. (This assumes you have an unfinished attic). If your roof were white, it would absorb less heat. However, less heat in the attic means less air being drawn in from the soffits. I have no numbers, but I would expect the temp difference would not be significant; more heat absorbed = more air pulled in = lowering temps ... I bet it wouldn't have a giant impact.
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ChubChub wrote: Use more? Probably. But I doubt it would be significant enough to matter. (This assumes you have an unfinished attic). If your roof were white, it would absorb less heat. However, less heat in the attic means less air being drawn in from the soffits. I have no numbers, but I would expect the temp difference would not be significant; more heat absorbed = more air pulled in = lowering temps ... I bet it wouldn't have a giant impact.
Only if a roof/attic is properly ventilated. I wager many are not. My house has black concrete tiles. Gets dreadfully hot on sunny day and there were/are only 5 turtle vents for quite a large area.

That said, sufficient insulation would make it a less-relevant point. It would be nice if one could harness the heat for use in winter and preheat water on the way to the hot water tank..

FWIW, many houses north of the Loire river in France (approximately divides the country into north and south) have black (usually slate) roofs while those to the south have terracotta roof tiles.
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thriftshopper wrote: Only if a roof/attic is properly ventilated. I wager many are not. My house has black concrete tiles. Gets dreadfully hot on sunny day and there were/are only 5 turtle vents for quite a large area.

That said, sufficient insulation would make it a less-relevant point. It would be nice if one could harness the heat for use in winter and preheat water on the way to the hot water tank..

FWIW, many houses north of the Loire river in France (approximately divides the country into north and south) have black (usually slate) roofs while those to the south have terracotta roof tiles.
Valid points for sure. I was assuming the roof is properly configured for the climate, but you're right, that is probably not a given (my house had vented soffits, but under those vents? Solid plywood. That was the opposite of fun to fix).

As for heating water: if you REALLY wanted to, you COULD do this. Basically all municipal water should be able to go as high as 28in x water pressure (in PSI). Put a giant tank in your attic, ensure the structure of your house can handle the weight, and you'd have ~60°C water "for free". Now, you'd probably need a circulating pump and a coil of pipes on the roof to get the recovery rate up, but it would work. Now, having that much water is a DIY tank above your entire living space? Not sure :)

If you only took showers while it is still sunny, you could feed the HWT with water the initially comes through some pipes on the roof. Having done this for quite a few pools, on a sunny day, you can turn 80°F water into 105°F water.

As an aside: I am realising how bad I am at switching between units.
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To boot, the membrane between the roof vents and attic were either not cut or had a hole cut in the wrong places so there was effectively no ventilation. There are large perforated soffits around the periphery but since heat rises...

Depending on geographic location, I would worry about pipes/tanks freezing for in-attic water heating, in addition to bursting and leaks (could happen anywhere). Just an idea but the practicality, or consequences of something going wrong are rather drastic.

My local plumbing wholesaler is clearing out a few remaining solar water heater components. Looks like "evacuated tube" is what we need for our climate.

http://www.apricus.com/solar-water-heaters-1/index.html
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thriftshopper wrote: To boot, the membrane between the roof vents and attic were either not cut or had a hole cut in the wrong places so there was effectively no ventilation. There are large perforated soffits around the periphery but since heat rises...

Depending on geographic location, I would worry about pipes/tanks freezing for in-attic water heating, in addition to bursting and leaks (could happen anywhere). Just an idea but the practicality, or consequences of something going wrong are rather drastic.

My local plumbing wholesaler is clearing out a few remaining solar water heater components. Looks like "evacuated tube" is what we need for our climate.

http://www.apricus.com/solar-water-heaters-1/index.html
Oh, this heating system would be summer only, and leaks would be a huge pain. I am not recommending you do it, just saying you theoretically could :). In July, where my only gas use is basically my HWT, the cost for NG is only $8.47 (+ fixed charge, but I'm ignoring that). So, if this magical system reduced my HWT cost from $8.47 to $5 (that's probably being generous), for the 6 months / year I could use it (max), I'd be "saving" $21/year. The cost of materials, and ballache of uninstalling/reinstalling it every year? Yeah, nah.

I will say, if you have a hottub whose water you're replacing every month, this system could have more value (and would not have to be installed inside your house).
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Jul 1, 2016
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thriftshopper wrote: I sent quite a bit of time travelling in France and wherever it was an option, staying in older buildings (i.e., pretty much older than century or two) where possible. One thing that struck me was the common use of shutters for doors and windows, not just for security but I presume as an insulation barrier.

Shutters would benefit during the heating season in at least two ways 1) stop most long-wave heat going out and 2) create an air insulation layer of some sort. During the cooling season, it will at least keep radiated heat out.

I guess the trouble is the cost, as well as the massive expanse (number, width) of windows in some houses. There's really no place in my current house to use shutters except in a handful of room. Windows generally have to be inswing too.
A practical compromise would be to use thermal-control window films with curtains. They're a nice in-between, it's something all homeowners with many south side windows should consider.

It's very economical to get started; $150-200 worth of materials (for "generic" quality films) for about 36 inch x 30 feet worth of film and basic installation kit.

Installation will take some time and patience; thorough cleaning of the glass surface and recommended to install at dawn/dusk before direct sunlight hits the glass for an simpler installation process.

The manufacturer specifications for the film speaks volumes; at the cost of about 50% incoming light, there is approximately an reduction of 50-60% incoming IR thermal energy; with 6-9% reflected and 40% ish absorbed by the film. Reduces heat loss in winters by 6-8% (may not sound like a lot, but adds up quickly once applies to ALL of your windows). Furthermore, as this is a passive process, it's working 24/7. I'd imagine this would add up quite quickly over a summer or winter.

There's plenty of film options too; from 5% to 90% incoming light reduction, reflective exterior, frosted, etc.
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The film option is a good one but sometimes it works when you don't want it to. e.g., in winter, you can't warm the house with solar energy (low sun does has a purpose, assuming your house has a good and relatively-unobstructed southern exposure). True, the heat loss to the outside might offset any solar heat gain, but that's what the shutters are for.

I have low e-coatings on the 3 sets of SE-facing French doors. Not sure how much winter solar heating one is losing but I guess the more-efficient sealing over generic french doors is a marked improvement.
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