I was chatting with the sales rep and they said that it doesn't stop the solar heating effect heat the room to today's maximum temperature, it just makes it take longer
But that's of no use at all if once the room has got to 32 degrees today, it doesn't cool overnight, and I start tomorrow still at 32 degrees
How do I keep my room cool (other than air con obviously) (Totally south facing, sun beaming down on it 14 hours of the day!)
close the curtains and windows by day, and open them at night. This works really well if house has a lot of thermal mass (concrete floors blockwork, fireplaces and chimneys) INSIDE the insulation layers.
Its not much cop if the house is made to modern standards out of balsa wood and cotton wool
is available for a non-daylight-robbery price from:
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solar films are £100-200/m)
It helps, but it's not a pancaea. The film reflects some proportion of the incoming solar radiation. The problems are:
- You're mounting this on the inside of the window (outside not accessible in my case). It reflects some of the radiation back into the double glazed unit. That means the heat it doesn't reflect but absorbs (which is does a fair amount - gets quite warm) goes into the room. If it was mounted on the outside that heat would mostly stay out.
- You can view solar insolation as filling a leaky bucket. Eventually the incoming flow will balance with the outgoing flow (because the room is hotter than the outside so the heat will leak out again). The film cuts the rate of incoming heat, but it doesn't eliminate it. That means the room may warm more slowly, but still warm.
You can slow the heat flow by adding insulation which will allow you to withstand a bigger temperature difference for longer, but not forever. For windows that means film, low-E glass, external shutters to reflect insolation.
There's roughly two challenges here. One is temperature changes through the day - warming up fast when the sun comes out, cooling rapidly at night, versus slower changes. That's the realm of thermal mass. If the average temperature is tolerable, thermal mass will smooth out the peaks and troughs (over days or months), and insulation will make the temperature changes less rapid. The flip side of that is insulation can make it harder to cool down once it has got hot.
The other one is heat soaking: when it is 30C outside even at night, there's nowhere for the heat to go. That means active cooling ie air conditioning. Here the insulation will prevent the heat getting back in again.
If you think about it for heating, you can have a super insulated house but it doesn't magically become warm by itself. You add heat sources (which might include people, appliances) to keep it warm. You also aim to trap the solar radiation that you do get to make the most of it as 'free' heating.
Cooling is the opposite, except that we don't have any existing 'sources of cold' so the problem is harder. Either you trap cool from eg the night time outside, or you actively pump the heat out. If it isn't cold enough in the night time, active cooling is the only option.
I fitted it years ago on west-facing windows. Quite easy but it dramatically lowers the light levels. OK on bright summer afternoon and it makes the sky and trees look more intense but in gloomy weather you need the lights on much earlier. There are different grades and tint colours depending on what percentage of light you want to stop. Choose carefully.
My current house is south-facing and In extreme I drape a big builders dust-sheet out of the two upstairs windows and use a wooden pole to create a sort of spinaker to shade the rear wall. very effective and In Oz everyone seems to have one tied to the eucalyptus trees in the garden.
have you thought of growing a passion flower or similar climber over the rear wall ?. This will massively reduce the solar gain on the brickwork and some of the glass.
Not at home, but at one customer site there is a long glass corridor linking two buildings, it used to *BAKE* in there in summer, they fitted the film and it made a huge difference, it did also cause a problem that birds would fly into it, leaving a dusty outline of themselves, so they had to put some decals of birds onto it, which I think stopped that.
Assuming ground floor , then a summertime screen of fast growing tall annual oe die-back perennial plants, in a line spaced a few feet from the wincow, echium, sunflowers , foxgloves, etc?? Even some tall grasses work quite well. Then perhaps green-wall coverings/creepers to the rest of the walls to reduce the solar gain there
Outside is theoretically possible, if it's worth the extra effort
Ok, that's my concern
insulation where?
realistically, replacing the windows is not an option
new glass panels perhaps
would be nice, not going to happen
There is no cooling at night
That's the problem.
last night with the rain it was colder outside overnight
but with windows open all night, the room cooled from 28 to 26.
So I start the day pretty much where I left off the evening before.
And this week is a small heatwave. Last summer, daytime temp reached 33.
I don't understand this reference to insulation
If everything were equal, the insulation in my house is such that it wouldn't warm up to the outside temp though the walls or windows by conduction.
But everything is not equal, I am south facing and my room is heated directly by solar radiation through the windows. Even with the curtains/blinds closed.
OK so that's the *only* solution?
Oh yes it does
Solar radiation means that I hardly have to have my heating on at all in the winter.
I'm not trying to directly cool the room
I'm trying to avoid it heating up by solar radiation.
Look at the numbers for the different films and see. Outside the film has to be more robust as it gets weather which is doesn't inside.
Any external surfaces. Walls, roof, floor.
Exterior film is likely to get a good way towards the performance of new glass. Again look at the numbers.
So if it not cooling at night because there is insufficient exchange of air with a cooler outside (in which case think about improved or mechanical ventilation), or because the outside is insufficiently cool enough to make much difference?
Any room is a system. The insulation and thermal mass of the walls play a part just as the solar gain of the windows do. You have to consider them all together.
(think about a tent - lots of solar gain so heats up rapidly, but no insulation or thermal mass so cools rapidly too as soon as the sun goes down)
If it's 30C inside and 30C outside no passive measure is going to help, because you can't make heat flow uphill without active refrigeration. If you can have something in the system that is cooler then maybe you can use that cold passively. That's easier in a cellar than in a flat.
That's trapping solar radiation as a source of heat, as I mentioned below. A Passivehaus is designed to optimise that trapping, as is a greenhouse. A windowless garden shed, even if super insulated, is not.
Your problem is that you're trapping solar radiation on the days it's too hot as well as the ones where it's too cold.
So either you block that solar radiation coming out (shutters, film, foil in the windows) or you pump the heat out.
what I was hoping for, given that we only have these heat waves for a short period, is a means of avoiding it getting to 30 on the inside, in the first place.
exactly
so my question was (still is) can I get a film (or any alternative that I can temporarily stick on the inside) that achieves that? - Shutters on the outside is never going to happen!
Outside shutters or blinds work well but can be prone to needing a lot of maintaining as well. It reminded me of another of those ever so numerous Tomorrows World ideas that seemed never to take off. A kind of glass that would be far more efficient at temperature control as the outer pane in double glazed units which could have its characteristics electrically controlled by tiny embedded microwires. They did have a lot of devices like that, and I suspect most soon tended to either cost too much to make or were basically unreliable in use. Brian
Yes, but there's no magical film that will block all heat while letting all the light through. It's your call as to how much of each you want, and the heat rise depends on what happens to the solar radiation once it's entered.
Here's a simple experiment. Next time there's a sunny day forecast, at night time cover your windows inside with baking foil so no light comes in. See how much the temperature rises in the daytime.
The foil is like the ultimate window film. If that is sufficiently cool for you, then a window film may help - a tradeoff of letting in some light in exchange for more radiated heat coming in. If it doesn't, the foil is blocking roughly 100% of incoming solar radiation and so film is not going to improve on that - the heat is getting in in other ways (eg conduction through the glass, air movement from outside, etc).
If this is a problem in summer only, it may be worth thinking about what you can do to block the radiation in summer but keep it in winter. For example close-fitting reflective blinds or panels that you only deploy in summer.
Film: 100 pounds to buy (for all three rooms), perhaps the same again to get "my" man to fit
Portable Aircon: 500-700 pounds capital cost, 20 pounds per week to run, for one room only. Plus the inconvenience of having it sit in the room even when not in use, as I have nowhere to store it
I can afford the aircon, but it seems to be overkill for 2 weeks of the year.
Much cheaper version if you don't care about appearance is a roll of the cheap stuff sold as holographic wrapping paper. Essentially just aluminised mylar film with complex patterns in it. Just hang it up and you will see how much difference it makes. The proper stuff will be better but by nowhere near enough to make up for the price difference.
We used this solution for our S facing home office during lockdown - otherwise the sun was too bright to see the computer screen!
That is sort of true. It slows the ingress of heat into the room by reflecting a fair proportion of the sunlight away. But a good reflector is also a poor radiator. You can do almost as well with white curtains.
Possibly better if you have opening lights at the top to let out the trapped warm air (better still is exterior shading).
It will also slow the radiation of heat away again so you need to open the windows at night to take advantage of the cool night air.
External window shutters is one solution that works really well in hotter climates or window shades that come out from the building. My S facing company office had those (designed in from the outset).
The thermal mass of my solid walled house is so great that in summer we can remain cool even in the hottest weather just by opening and closing the odd window. Staying warm in mid winter is more of a challenge.
I currently have the windows in one room covered with blackout material to stop the early morning sun waking me up
but in the extreme heat wave last year, that didn't stop the sun heating the room up (I could tell it had been heated through the windows rather than transference from the other rooms by feeling the temperature of the inside of the material)
So are you saying that if I put reflective foil on the outside of those blinds it will work better? I need a permanent solution to this problem anyway as keeping then stuck to the windows on the window when I don't need them has caused mould to grow on the frames.
A black surface is the worst you can have in your case. I would recommend either reflective or white. A white surface will reflect most light back outside.
Most UV and mid and far infrared is stopped by glass. Something like space blanket material will reflect a lot of the IR too.
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