We should have installed air conditioning… now what?

[SteamyTea]

Just now, Adsibob said:

Have a look at the graphs I just posted, tell me if that is the picture of success? Am I expecting too much?

Well it is cooler than the outside air.

Was your MVHR on summer bypass?

[Adsibob]

12 minutes ago, SteamyTea said:

Well it is cooler than the outside air.

I don’t have an external thermometer to log that data, but I recall that on Friday the bbc was reporting that it was 31C in London, which is about the same as the max temp that was reached in my study. Looking at this in more detail, it seems I’m achieving a decrement delay of about 6hr, whereas I had designed for 10hr (more not being possible), but it’s not clear. I probably need to get an external thermometer and track my local weather the way Tado is tracking my internal “weather”.

12 minutes ago, SteamyTea said:

Was your MVHR on summer bypass?

I activated it on Tuesday. Maybe I should fiddle with the settings, but I didn’t think it could do much more than lower internal temp by a degree or so?

 

Edited June 19, 2022 by Adsibob

[SteamyTea]

37 minutes ago, Adsibob said:

Have a look at the graphs I just posted, tell me if that is the picture of success? Am I expecting too much?

Got the laptop out so I can see the charts better.

I am not sure which part of London you are in, though I don't think it will make much difference to OAT, so shall just pick a random station towards the centre, see what they were recording.

[ProDave]

26 minutes ago, Adsibob said:

Looking at this in more detail, it seems I’m achieving a decrement delay of about 6hr, whereas I had designed for 10hr (more not being possible), but it’s not clear

What exactly is your wall make up?  Our calculated decrement delay time was 13 hours and it certainly seems to be close to that, our house maintains a pretty constant temperature only warming up or cooling down slowly.

 

You need to eliminate solar gain as the culprit so even if you can make temporary exterior blinds to prove a point e.g even something as simple (on a dry day) as cut a large piece of cardboard and tape that to the outside of the velux windows for a day to block the sun out completely.

[SteamyTea]

Right, had a look at this WU station:

https://www.wunderground.com/dashboard/pws/ILONDO480/table/2022-06-17/2022-06-17/daily

 

Seems temperatures peaked at 33.7°C and had an average of 25.7°C, minimum was 16.7°C.

You also had an hour, 12:09 to 13:04, when the solar radiation was over 900 W/m².

That is really quite impressive.

So I think most houses would struggle with that.

 

 

[Adsibob]

4 minutes ago, ProDave said:

You need to eliminate solar gain as the culprit so even if you can make temporary exterior blinds to prove a point e.g even something as simple (on a dry day) as cut a large piece of cardboard and tape that to the outside of the velux windows for a day to block the sun out completely.

This is an incredibly good idea!

7 minutes ago, ProDave said:

What exactly is your wall make up? 

Here is the build up of the loft, although I don’t think the “dormer cheek” build up is relevant, because it is the other room in the loft which is bounded by the cheek. So peripherally relevant (as that room is also too warm), but not directly.

[Radian]

17 minutes ago, ProDave said:

You need to eliminate solar gain as the culprit so even if you can make temporary exterior blinds to prove a point e.g even something as simple (on a dry day) as cut a large piece of cardboard and tape that to the outside of the velux windows for a day to block the sun out completely.

 

Almost as cheap and possibly nearly as effective and maybe permanent solution is to apply a UV blocking film on the inside of the glass. Amazon have plenty to chose from for around £10-£20 a roll. With plain glass the short-wave UV in the sunlight gets through and is converted into longer wave IR when it hits interior surfaces therefore blocking UV at the internal face of the glazing can be just as effective as external treatments. The coated glass operates on the same principle but the coating is usually much thinner to be more aesthetically neutral.

 

I'm going to try some on my SE facing Velux - there's a choice of silver or black tint. I fancy black to blend in better with the slate roof.

[SteamyTea]

Is the roof facing the street on the side that it gets the afternoon sun?

You could paint it white, or cover it in mirrors.

Other coatings are available.

 

Light-filtering paint cools your home when exposed to hot sun

 

TECHNOLOGY 9 October 2017

By Sandrine Ceurstemont

 

A cool feature if painted right

polarica/Getty

 

The sun itself could soon become a low-cost air conditioner. A high-tech paint that actually cools when exposed to sunlight can provide a better way to chill buildings – and perhaps even solve the long-standing problem of cooling things in space.

In hot weather, electricity consumption soars as people turn on the air conditioning, pushing the grid to its limits and raising energy bills. Now Yaron Shenhav and his colleagues from SolCold, a firm based in Herzliya, Israel, have come up with an alternative that doesn’t require electricity. “It’s like putting a layer of ice on your rooftop which is thicker when there is more sun,” he says.

The technology is based on the counterintuitive principle of laser cooling, in which hitting specially designed materials with a laser can cool them by up to 150°C. It works because molecules in these materials absorb photons whose light is of one frequency while spontaneously re-emitting higher-frequency photons, which also carry more energy. Since energy is lost, the temperature of the material is reduced in the process.

 

Mounting lasers on your roof wouldn’t be very practical, though, so Shenhav wanted to see if he could tweak the technique to make it work with sunlight instead. “Heat from a building could be absorbed and re-emitted as light,” he says. “As long as the sun is shining on it, it would be continuously cooled.”

The problem is that the sun’s spectrum is much broader than that of laser light – a focused beam with a narrow range of frequencies. So the team had to create a material that could do the same trick using several frequencies of scattered light. They came up with a paint made up of two layers: an outer layer that filters out some of the sun’s rays and an inner one that does the heat-to-light conversion, cooling itself below the ambient temperature.

So far, the material has been successfully tested in the lab, where the researchers have found that the effect is more pronounced on metal roofs than on concrete, and works best over rooms with low ceilings. Simulations show that a room on the top floor will feel up to 10°C cooler than with the paint applied if applied to a roof of a house than without the coating. The team will conduct pilot tests on buildings within two years.

 

People already use white cooling paints to scatter and reduce the amount of heat buildings absorb. However, they can’t actively reduce the temperature in the building, whereas SolCold’s paint can, says Eran Zahavy at the Israel Institute of Biological Research, who was not involved in the research.

Cut the air conditioning

The new paint isn’t cheap, costing about $300 to coat 100 square metres. Shenhav and his team think the early adopters will be large commercial buildings like shopping malls and stadiums. There, the coating could lower energy consumption by up to 60 per cent, massively reducing bills and carbon emissions.

It could have other knock-on environmental benefits as well. The continuous use of air conditioning in already hot areas like Phoenix, Arizona, creates urban heat islands which have been linked to steadily rising temperatures in such cities. With the new paint, “buildings would be able to install much smaller air-conditioning units,” says Shenav.

The paint’s use isn’t limited to this planet: it could solve the significant challenge of how to cool objects in space. That might seem counterintuitive given the frigid temperatures there, but the problem is that there is no air to carry heat away from an object. Currently, the ISS uses reflective fabric to ward off radiation from the sun, and internal heat exchangers to get rid of excess heat produced by equipment. “With our technology, heat is transferred through light,” says Shenhav. “Space applications are a big market for us.”

The team will be presenting their work later this month at the Hello Tomorrow technology summit in Paris.

 

 

Whitest paint ever reflects 98 per cent of light and could cool homes

 

ENVIRONMENT 15 April 2021

By Matthew Sparkes

 

An infrared camera shows how a sample of the whitest paint (the dark purple square in the middle on the right) cools the board below ambient temperature

Purdue University/Joseph Peoples

 

An extremely white paint that reflects 98.1 per cent of sunlight can cool itself by radiating heat into deep space. It could help keep buildings cool, potentially replacing energy-intensive air conditioners.

Xiulin Ruan at Purdue University in Indiana and his colleagues previously developed an ultra-reflective paint using calcium carbonate particles that reflected 95.5 per cent of sunlight. They have now improved on that by using barium sulphate particles in a paint that reflects 98.1 per cent of sunlight.

This new ultra-white paint absorbs less than half the amount of energy from the sun as the previous paint. Standard commercial white paint absorbs between 10 and 20 per cent of sunlight energy.

 

The amount of sunlight absorbed by the new paint is lower than the amount of energy it radiates through our atmosphere and into deep space, so the material actually becomes cooler than its surroundings. The team plans to carry out experiments with painted tubes carrying water and hopes to create an electricity-free refrigeration effect.

The team hopes that the paint can lower global carbon emissions as houses coated in the paint would need less air conditioning. If the paint is used on a 930 square metre roof, the cooling effect could be as high as 10 kilowatts, which the team says is more powerful than a standard air conditioner.

Read more: Infrared-reflecting paint can cool buildings even when it is black

Ruan says there is a double-pronged positive effect because the paint sends energy away from our planet. “We send the heat to space, we’re not leaving the heat on Earth,” he says. “Traditional air conditioners leave the heat on Earth’s surface, it’s just moved from the inside of your house to the outside.”

 

The team calculated that if 0.5 per cent to 1 per cent of Earth’s surface was covered in this paint, for instance by coating roofs with it, the total effect would reverse global heating to date.

The painted surfaces will need to be kept clean of dust and dirt to retain their reflective properties but the team is working on ways to make it shed particulates.

Ruan is now working on an even more reflective material but says that there may be diminishing returns. “Pushing to 100 per cent is hard. You will get 19 watts per square metre more cooling benefit, so practically it may not be that attractive given the cost,” he says.

 

Journal reference: ACS Applied Materials & Interfaces, DOI: 10.1021/acsami.1c02368

 

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White paint on a hot tin roof

 

25 March 1995

By Rosie Mestel

HAIDER Taha has been hard at work. He’s slapped white paint and light-coloured tiles on millions of rooftops all over Los Angeles and the sprawling communities surrounding it. He’s replaced thousands of miles of black, asphalt roads with surfaces the colour of weathered concrete. He’s sneaked into the gardens of millions of private homes and planted trees to shade their roofs. Taha’s heroic efforts have cooled areas of LA by as much as 4 °C, slashing air conditioning bills and ridding the region of a sizeable chunk of its air pollution. Not bad for a couple of years’ work.

Sadly for southern Californians, Taha’s city is not the real LA, where the smog is still legendary and summers get hotter year by year. Instead, the cooler version comes from a giant computer simulation started in 1993 by Taha and colleagues at the Lawrence Berkeley Laboratory in Berkeley, California, and the University of California, Los Angeles. Taha’s trees are fake, and the new roofing is imaginary, digitally daubed onto houses and factories. But one day, says Taha, real cities could follow suit.

To that end, scientists around the US are figuring out cost-effective strategies for combating the so-called “urban heat island effect” – the tendency of cities to get warmer as buildings and roads engulf the countryside. They’re testing real houses with trees for shade and coatings that reflect sunlight; they’re analysing new roofing materials and pinpointing the species of trees that would help or hinder their efforts. “The urban heat island is a man-made effect,” says Hashem Akbari, leader of LBL’s Urban Heat Island Project. “And if man is doing it, then man can undo it.”

Take, for instance, what development has done to LA. In the mid-1800s, before this desert area was built up, summer highs averaged 39 °C. Then, as river waters were diverted to the basin and vast orchards of fruit trees were planted, the temperatures fell to a nadir of 36 °C by the 1930s. Thereafter, as orange trees made way for houses and roads, temperatures climbed back to 39 °C. And they’re still rising, as building continues. Nor is this effect unique to LA: many cities, including New York and Mexico City, are up to 3 °C hotter on a summer day than the surrounding countryside.

 

Akbari and Arthur Rosenfeld, former director of the Center for Building Science at LBL, were the first to convince the research community of the science behind these temperature changes, in the mid-1980s. Black asphalt roads and roofing absorb more sunlight than open fields, sucking up the Sun’s heat, they said. Trees and vegetation, once cleared, can no longer cool the air via the water that evaporates from their leaves. Reversing this trend is part of President Bill Clinton’s Climate Change Action Plan announced in 1993, which Rosenfeld is helping to develop as a senior advisor at the US Department of Energy.

Real cool

How do you cool a city like LA? Trees that shade houses keep the sunlight away and the houses cooler. White paint and other reflective coatings deflect much more visible and infrared sunlight than common roofing materials such as black asphalt shingles, so houses gobble up less energy on air-conditioning. Trees, meanwhile, are continuously releasing water from the pores in their leaves, which cools the air as it evaporates. The end result? Hopefully, a cooler city.

 

And a cleaner city, too. The region’s factories, refineries, power plants and 8 million vehicles spew out a cocktail of chemicals, including hydrocarbons and nitrogen oxides. These react with sunlight to form a smorgasbord of pollutants that blankets the south coast air basin (LA and the cities surrounding it) – the most dangerous of these, from a health point of view, is ozone. Chemicals react faster when heated, so the higher the temperature, the faster the smog forms. “There’s never been a smog alert when the average daily temperature was below 21 °C,” Rosenfeld points out.

Not only that, but the array of organic chemicals evaporating from gas stations and cars, paints and coatings on buildings, fuel and chemical storage tanks, wafts up in even greater quantities when the city is hot, adding to the smog.

Just how much better would things be with decent, reflective roofing and roads and well-placed trees? To figure that out, Taha and colleagues pored over satellite images of the south coast air basin to determine where the trees were and which parts of the region were residential, industrial or undeveloped. And they flew over the basin to estimate the reflectivity of different locations.

They then divided a map of the region into 2600 portions, and estimated how much added vegetation and increased reflectivity – or “albedo” – each portion could take. When they simulated the effects of adding moderate amounts of trees and white roofs (up to 15 per cent of all changes thought to be possible), the average summer temperature in the basin dropped by 4 °C, although the exact change in temperature varied from place to place. Estimated summer energy savings amounted to between $100 000 and $200 000 per hour.

Next, Taha fed his data into the Urban Airshed Model, which is widely used by air quality officials. This calculated the effects of these altered temperatures on the region’s smog, based on factors such as wind patterns, moisture, temperature, and where the region’s pollutants are released. This time, he found that a moderate change in albedo reduced the smog – getting rid, on average, of 5 per cent of the ozone that exceeds the region’s air quality standards. Planting a moderate number of trees reduced the smog by 3 per cent.

If you add together the effect of the trees and reflective materials, he says, the figure comes out at 10 per cent. “It’s a huge effect,” says Rosenfeld. “It’s the equivalent of getting about three million cars off the roads.” Taha notes, though, that these numbers are far from uniform across the basin, mainly due to differing wind patterns. His print-out of the results looks like a haphazard chess board of different smog levels, with some unlucky places having worse smog than before.

But simulations have their limitations. “Models are models – they only do what you ask them to do,” says Taha. “And the types of studies I’m doing cannot be validated – no one has painted LA white for me to double-check my results.” And even if his findings are right on target, implementing the “cool cities” scheme has its complications. By planting the wrong kinds of trees, cities may do the equivalent of adding polluting cars to the area. Many trees emit highly reactive hydrocarbons, terpenes and isoprene, that react with nitrogen oxides and contribute to the smog. Today trees may give off as much as 10 per cent of the polluting hydrocarbons in the LA region.

And so one strand of the project is to figure out which trees are naughty, and which nice, from the point of view of smog. This task has fallen to Arthur Winer, director of the environmental science and engineering program at UCLA. Winer has studied tree emissions for 15 years and is collaborating with the LBL group. Spreading the word about low-emitting and high-emitting trees is tricky, he says, without being perceived as a tree-hater.

“When I first started to talk about this work to urban forestry people, at times – looking out at the audience – I thought they were going to start throwing tomatoes, or take a big hook and haul me off stage,” he says. “People love trees. They have their favourite trees and they get upset to be told that an oak or a weeping willow or a eucalyptus is a ‘high-emitting tree’.”

But the fact remains, he says, that the highest emitters, including weeping willow, release ten thousand times more terpenes and isoprene than the lowest emitters, such as ash. And while nobody’s suggesting that the thousands of trees already standing should be chopped up for firewood, planting high emitters en masse will not help improve air pollution. Taha’s “good” simulations were performed with low-emitting trees. But when he used moderate emitters in his model, ozone concentrations in certain areas increased by as much as 25 per cent.

Planting spree

Already, large-scale planting schemes are taking root in US cities with a view to saving energy as well as creating a more leafy environment. California’s Sacramento Municipal Utility District, for instance, is well on the way to its goal of planting 500 000 trees by the year 2000 – all of them, SMUD maintains, low-emitting species. LA has similar schemes on the drawing board.

And so each of the 375 species of trees and shrubs that are commonly planted in the LA basin must be rated, which is no easy task. For each measurement, the scientist must encase a branch in a transparent, gas-tight bag, take samples, and run the sample in a gas chromatograph to quantify the terpenes or isoprene. The leaves must be stripped and dried, to measure leaf mass. Variation from day to day and branch by branch is great, due to a host of factors, such as how much sunlight falls on any particular branch. No wonder, then, that only 150 species – measured by Winer and others – have been tallied. For the other species, Winer has classified them in high, low, or medium groups based on the emission properties of their nearest measured relatives.

Meanwhile, other researchers are doing what they can to test all these theories in the field. For instance, Akbari’s team has measured air-conditioning costs before and after surrounding houses in Sacramento, California’s state capital, with 6-metre shade trees loaded onto flat-bed trucks, and coating the roofs with a reflective, white, plastic polymer. The researchers found that the air-conditioning in the houses used 40 per cent less energy, with the reflective roofing causing 50 to 60 per cent of the saving, on average.

Experiments in Florida gave similar figures. Jack Parker, professor of chemistry and environmental science at Florida International University in Miami, planted vegetation round a childcare centre, then monitored the costs of air conditioning as trees and shrubs matured over the years. The centre reduced its air conditioning costs by 58 per cent at the height of summer. Danny Parker, a senior research scientist at the Florida Solar Energy Center in Cape Canaveral, monitored houses all over Florida before and after coating their roofs with bright white polymers. He saw average air-conditioning savings of 19 per cent, ranging from 3 to 43 per cent depending on insulation and roof type.

Measuring the direct effects on houses is one thing. But it’s much trickier to test whether the vegetation and reflective surfaces will alter temperatures of entire neighbourhoods. That’s because the effects may be overshadowed by day-to-day and place-by-place changes in the climate.

“You’re moving towards ‘weather’ when you’re trying to measure these mesoclimates,” says Danny Parker. “These are very inscrutable systems.” Nonetheless, researchers are gamely trying to gather data to see whether more trees and white roofing produce measurably cooler air temperatures. The LBL group, meanwhile, has shown that local temperature differences can definitely be detected in the more uniform desert climate. They have monitored the air above New Mexico’s White Sands National Monument, a vast stretch of highly reflective sand, and compared it with that of the surrounding desert. They found that the morning air, was 3 °C cooler over the reflective sand.

Growing interest

But neighbourhood effects or no, the house-by-house energy savings seem clear. Even the utility companies – who say they want their customers to save energy so they don’t have to build new power plants – are getting interested in roofing and trees. Air quality officials are showing interest too. “It’s an exciting idea that has to be pursued,” says Bernard Bloom, air resources engineer with the Montgomery County Department of Environmental Protection, in Rockville, Maryland. He is helping to develop plans to reduce pollution in the Washington DC area. “Taha has shown that maybe we can knock off 5 to 15 parts per billion ozone for each 1 °C drop in temperature, which would be about 25 per cent of our reduction need in Washington. It’s very significant.”

But there are still many questions to be answered, Bloom adds. It’s not clear, for instance, if other cities would behave like LA. Cities that have colder winters will have to make sure that houses don’t become more chilly in the winter; reflective roofing will absorb less sunlight when it’s cold outside as well as hot. This might cause energy demand to increase in winter, offsetting energy savings in the summer. If that’s so, says Bloom, the answer might be to develop “smart” roofing materials that reflect sunlight in the summer but switch to absorbing it when temperatures fall past a critical level. And such substances do exist.

It’s also important, he says, to ensure that reduced summer temperatures don’t alter air patterns so that pollutants hug closer to the ground, increasing ozone in cities. Taha’s simulations in LA took such changes into account and showed that pollution plummeted nonetheless. But every city should be modelled in turn, argues Bloom.

Another problem is that muck tends to build up on roofs and roads, and in humid places, like Florida, roofing becomes progressively streaked with algae and fungi. How well will sunlight be reflected when this happens? To get round the fungus problem, Danny Parker is developing paints that use zinc oxide, which acts as a fungicide and algicide, as a partial substitute for titanium dioxide, the conventional white pigment in paint.

And what if people don’t want bright cities, with gleaming white buildings as far as the eye can see? In fact, cities don’t have to be white to be cool. “We don’t have to make LA look like Casablanca,” says Rosenfeld (although most LA residents would probably consider this an improvement). While roughly half of sunlight’s energy is in the visible spectrum, most of the rest is in the infrared. By tinkering with their raw materials roofs can be made to reflect infrared and thus be cool even though they’re not white. Even a black asphalt shingle, which reflects 5 per cent of the Sun’s rays, can be made 11 °C cooler at noon if covered by a coating that reflects in the infrared.

Which just goes to show that you can’t just look at a substance and know what its reflectivity will be, says Paul Berdahl, a materials scientist at LBL. “I think we perhaps know more about the solar reflectance on the surface of Mars than we do about the solar reflectance of the roofs of our buildings,” he says.

His group has found, for instance, that a so-called “white” asphalt shingle which is really asphalt covered with tiny white stones – is actually fairly hot. With a dark undersurface, it reflects only 30 per cent of sunlight compared with 80 per cent for a good white paint. Two red terracotta tiles that look identical may in fact reflect different amounts of light, due to greater or lesser amounts of magnetite, which absorbs a lot of infrared.

Eliminating these impurities would be one way to make roofing cooler, says Berdahl. Another way would be to alter the size of pigment particles, since substances tend to reflect more light when the particles are of a certain size. Smoother roofing surfaces also reflect sunlight better, since a photon is more likely to be deflected cleanly away if the surface is flat, rather than hilly.

Heat labels

Ultimately, the LBL group would like to see the day when the solar reflectance of all roofing materials is well understood, and when minimum standards for reflectance are built into the California building and material codes. They’re working on a ratings scale right now, in collaboration with the American Society for Testing Materials. They’ve also been talking to roofing manufacturers, who are interested in devising temperature labels for paints and other materials.

Urban heat island projects are taking off. Public utilities around the country, such as Sacramento’s SMUD, are beginning to put their money into tree and roofing efforts. Southern California’s South Coast Air Quality Management District is starting to incorporate the LBL data into air quality policies. By encouraging home owners to use the right materials when they reroof their houses, and by promoting low-cost, volunteer programmes to plant trees, Rosenfeld, Akbari and colleagues think they can make cool city measures highly cost-effective. Roads and roofs must sooner or later be replaced, at which time new reflective coatings can be added at little cost. If implemented nationwide, these could help clean the air and save $10 billion in annual energy costs within 20 years.

“This has the chance of being the most astoundingly productive single thing that you can do to improve air quality,” says Rosenfeld. “The country’s going to a lot of trouble to try to figure out how to make hybrid cars or clean cars – and this is a cheaper way to do it. Frankly, in terms of potential, it’s probably the nicest, most important single piece of environmental science on the market.” (see Diagram)

 

[ProDave]

30 minutes ago, Adsibob said:

Here is the build up of the loft, although I don’t think the “dormer cheek” build up is relevant, because it is the other room in the loft which is bounded by the cheek. So peripherally relevant (as that room is also too warm), but not directly.

Similar to us except we have 100mm wood fibre board on the outside of the rafters, making it a warm roof and no need for the ventilation , and 200mm between rafters.  But no PIR layer.

[Radian]

On 18/06/2022 at 11:35, Adsibob said:

SN70/30 glass

 

From the spec "Ultraviolet Transmittance of UV  11 %" Peak Solar irradiance is around 1kW/m² 

 

You say your roof windows are 134cm X 98cm (1.3m²) and 134cm x 160cm (2.1m²) or around 3.4m² in total. At 11% transmission this would equate to a heat source of no more than 380 Watts. Of course it will depend on the area facing the Sun at any given time.  It doesn't sound like much but I have roughly half that area in my worst hot spot and it does push the temperature up by a few degrees. This is when all your insulation starts working against you!

[SteamyTea]

7 minutes ago, Radian said:

Of course it will depend on the area facing the Sun at any given time

I made a spreadsheet up once to work out from the absorption/transmission and reflectivity due to angles how much energy comes though a given area of glass.  Did it for our @Jeremy Harris, so was a few years back.

I may have it on a backup somewhere (I am overdue a new main backup), shall have a look if I remember.

 

One of the problems with solar gain is that it is soon forgotten in the UK.  3 sunny days and a thunderstorm and summer is over.

Though last year we had, down here in Cornwall, an extreme heat wave warning (the calculation is nuanced for a heat wave).  I covered my SW facing windows (half my wall area) in tin foil.  Worked brilliantly, room dropped 10°C.

[Onoff]

1 hour ago, SteamyTea said:

I covered my SW facing windows (half my wall area) in tin foil.

 

Stops "them" listening in too 👍

[SteamyTea]

37 minutes ago, Onoff said:

 

Stops "them" listening in too 👍

Stops the neighbours seeing what I am doing.

[Onoff]

4 minutes ago, SteamyTea said:

Stops the neighbours seeing what I am doing.

 

That's not Windolene...

[SteamyTea]

Back to the original problem.

How hard would it be to plumb in a portable A/C unit to the MVHR?

Cheap solution for the few days a year it is needed and I am sure enough airflow can be generated to cool enough air.

[Thedreamer]

The exhaust air source heat pump are not popular here, but if I had built our home in the south of England I would have investigated whether it would be possible to divert the cold air into the house during the summer. 

 

 

[Adsibob]

58 minutes ago, SteamyTea said:

Back to the original problem.

How hard would it be to plumb in a portable A/C unit to the MVHR?

Cheap solution for the few days a year it is needed and I am sure enough airflow can be generated to cool enough air.

Interesting idea, but there is another thread on here which confidently concludes that adding cooling to MVHR only reduces the temp by a degree or two because airflow is so low with MVHR. I have radial ducting, so presumably if i did add active cooling to just those ducts, I could just increase the airflow to the two hot rooms, and increase the exhaust from the bathroom on that floor to balance it?

[Adsibob]

 

4 hours ago, SteamyTea said:

Whitest paint ever reflects 98 per cent of light and could cool homes

 

ENVIRONMENT 15 April 2021

By Matthew Sparkes

 

 

 

Doh! We went for clay tiles in a dark grey colour, almost black. Actually I’m in denial, they are black!

[saveasteading]

My house in the SE does not get hot in the summer.

This is due to the design, where concrete tiles catch the direct sunlight, and a lot dissipates as convection.

then there is an attic, which gets stupidly hot. then 200 of fibreglass.

followed by high ceilings and it is much warmer high up.

Opening of doors at opposite sides can help, or hinder so need thought and control.

Leaving the doors open into the evening cools the fabric down ready for the next day.

 

Shutting curtains to keep the sun out helps a lot. Logically all the light, and energy is entering the room. Presumably some reflects back out and the warm air locally  doesn't spread round the room....not sure how it works but it does.

 

So just do all that to your existing house and it is solved.

If my problem was an office in the loft then I would be stuck, and no amount of cooling would work. How many days is this a problem?

Temporary transfer of the office? Totally blank the windows. Purge the air overnight.

[SteamyTea]

8 hours ago, Adsibob said:

but there is another thread on here which confidently concludes that adding cooling to MVHR only reduces the temp by a degree or two because airflow is so low with MVHR.

Yes, in normal operation you only need a small airflow.  This is mainly a noise issue, but a greater amount can be forced though on special occasions.

Alternatively, as you have UFH, how about fitting a chiller unit to that.  It would look very similar, identical in fact, to an ASHP.

[joth]

13 hours ago, Adsibob said:

14 hours ago, SteamyTea said:

Was your MVHR on summer bypass?

I activated it on Tuesday. Maybe I should fiddle with the settings, but I didn’t think it could do much more than lower internal temp by a degree or so?

 

I forget what Tuesday was like, but if it's hotter outside than inside you want to turn OFF the summer bypass. This way the heat exchanger is activated "in reverse" to cool down incoming air by "recovering" coolness from the outgoing air.

 

Summer bypass should only be active when the indoor temperature is above target AND the outdoor temperature is lower than indoors.

 

Happily for me my MVHR handles all that automatically. Otherwise I'd have used Loxone to automate it (basically same algorithm as I already made for skylight automatic stack venting control)

 

 

[Ferdinand]

15 hours ago, Onoff said:

 

Stops "them" listening in too 👍

It's that time again. 🙂

 

 

 

[Ferdinand]

5 hours ago, SteamyTea said:

Yes, in normal operation you only need a small airflow.  This is mainly a noise issue, but a greater amount can be forced though on special occasions.

Alternatively, as you have UFH, how about fitting a chiller unit to that.  It would look very similar, identical in fact, to an ASHP.

I have not met separate chiller units for ufh.

[Adsibob]

5 hours ago, joth said:

 

I forget what Tuesday was like, but if it's hotter outside than inside you want to turn OFF the summer bypass. This way the heat exchanger is activated "in reverse" to cool down incoming air by "recovering" coolness from the outgoing air.

 

Summer bypass should only be active when the indoor temperature is above target AND the outdoor temperature is lower than indoors.

 

Happily for me my MVHR handles all that automatically. Otherwise I'd have used Loxone to automate it (basically same algorithm as I already made for skylight automatic stack venting control)

 

 

My summer bypass is also set to automatic. I had a quick look at the status and it says:

 

Bypass State: OPEN

Inlet temperature: 19.7C

Outlet temperature: 22C

 

Does the fact that the bypass is "open" mean it is bypassing the heat exchanger and working as expected?

[saveasteading]

Interested in what people think, but I reckon 26C is not too hot indoors, and aircon is un-necessary.

If that feels hot then our bodies don't take long to adapt.  eg Mediterranean residents wear anoraks and jeans until the temperature is 20plus.

Northern types think 18 is hot, and might have to take a jumper off.