Why does the house get so hot at night?

Our house is about 7 years old. Outer red brick walls, cavity insulation, aero type blocks for inner wall, dot and dab plasterboard finish.

By day the house is reasonably comfortable, save the conservatory. But as night comes the house starts to warm, especially upstairs making the smaller rooms really stuffy.

Anyone know why this is and how we might stop it?

We have added an extra layer of insulation in the loft but this has not helped much.

Reply to
garym999
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On Sun, 08 Jul 2007 23:37:52 -0700 someone who may be garym999 wrote this:-

For a full diagnosis the orientation of the house, shading and room layout would be needed.

It is probably simply the hot air rising over the day and you notice it when you go upstairs to bed (presuming the bedrooms are upstairs).

If it is then try opening some of the windows on the ground floor and top floor slightly during the day. Opening them wide is not necessary. This will produce a gentle current of air which will limit temperature rises. In particular try opening the windows on the shaded side of the ground floor and sunny side of the top floor. Obviously leave the internal doors open. This may be difficult if the house is unoccupied during the day, but opening them this way in the evening may help and you can experiment at the weekends.

Reply to
David Hansen

Insulation keeps heat in... But I guess you close the windows at night even if they are open during the day. This will also trap any heat. As Mr Hansen says open windows a little low down on the N side and high up on the S. Draw the curtains on the south side during the day.

Reply to
Dave Liquorice

*envy* How do you get the house so warm?

Does the conservatory act as a heater? Can you close the doors to it to prevent heat flowing into the house?

Reply to
Mogga

The key to keeping houses cool in summer is to SHUT the windows by day - and the curtains - and OPEN them at night.

Reply to
The Natural Philosopher

The rear of the house, with the conservatory faces NNW. Of the four bedrooms one is to the rear, others to the front. The master bedroom windows are open all year and the radiator is never on.

Upstairs by day is fine. Early evening is OK but by late evening the difference is staggering. I know heat rises but I thought extra insulation in the loft would help prevent the build up in there. As we use the loft and it is boarded out I stapled Airtech to the joists. And that has knocked the temp in the loft down a lot.

"*envy* How do you get the house so warm?" Wish I knew. We brought the house off plan and I don't think it was built to any exacting standards, there are no cavity closures that I know of. If anything there is a draught blowing behing the dot and dab.

I have wondered about the conservatory build up as this does get real hot and as it is joined to the lounge you feel it in there too. but having the doors open lets it all blow away.

Reply to
garym999

David Hansen coughed up some electrons that declared:

That is the conclusion I came to as well - my modern well insulated house is horrid by evening upstairs in summer.

My trick was to open all the upstairs windows wide as soon as I come in after work (or just after supper). By bedtime most of the stored heat has dissipated and the air is fresh again.

Unfortunately, my wife's hayfever has kicked up again, so it's back to being a steamed dumpling. I'll try your method next, David.

Cheers

Tim

Reply to
Tim Southerwood

But that would trap the heat underneath, where you don't like it ...

Reply to
Mary Fisher

On Mon, 09 Jul 2007 10:38:17 +0100 someone who may be Tim Southerwood wrote this:-

Insulation slows down heat coming in through the walls and ceiling and so contributes to keeping buildings cooler in summer.

However, it does not stop radiation through the windows and if there are large areas of unshaded southward facing glazing then the heat this produces will be slowed from escaping through the upstairs walls. The answer to this is to deal with the glazing, and/or limit the solar temperature rise by ventilating.

Reply to
David Hansen

On Mon, 09 Jul 2007 10:20:08 +0100 someone who may be The Natural Philosopher wrote this:-

If the windows don't allow much sunlight through. Otherwise the sensible approach is to limit the solar temperature rise by ventilation during the day. Cool air from the side of the building away from the sun should be let in at low level to get the maximum cooling.

Remember that sunlight falling on (internal) curtains will cause a temperature rise within the room.

At night the ground, warmed by the sun during the day, is giving off relatively hot air and it makes little sense to draw this into the building.

Reply to
David Hansen

Curtains are not noted for their inherent transparency.

Otherwise the

Not in this house,. With air temps up to 30C outside, and internals nearer 25C, we don;t want any of that outside air coming in thank you!

Cool air from the side of the building

No, in the space between the curtains and the windows.. you DO have insulating curtains I hope..

Not at 3.a.m. it ain't.

Reply to
The Natural Philosopher

at low level to get the maximum

The philosopher is right on this one. And it goes further too. If you vent the house all night long, the temp of the fabric of the building drops, (not the air temp, which is a different beast) and this reduces the daytime temp rise, as the brickwork starts off colder.

This can also be done effectively during the evening if (and only if) you use proper control system. Waving your hand out the window and saying which is warmer leads to a totally ineffective result.

A differential thermostat plus fan can thus be used to knock a few degrees off the house temp most of the time. Worked very well at last place.

Windows that lock in the open half an inch position can be useful for this.

Resulting hay fever can be dealt with by wet filtering the incoming air - but dont let the cloth dry out or the dust is released. Put it in the wm while wet..

NT

Reply to
meow2222

Interesting.

I'd think it's sunshine/solar radiation falling on the outer surface of the wall. Depending on the materials and construction, this can make the outer face ludicrously hot. This heat takes some time to wend it's way through the structure, usually several hours. I'd suggest looking up tables for incident solar radiation in the CIBSE guides; I think there was also a factor called summat like suntime, used to estimate the time delay before the solar radiation incident on the outer wall surface made its appearance in the occupied space.

Depending on the affected wall area, you could slap up some foil-faced insulation to assess whether that is the cause. If not, I'd be looking at nuisance heat emissions from the heating systems.

Reply to
Aidan

On Mon, 09 Jul 2007 14:51:42 +0100 someone who may be The Natural Philosopher wrote this:-

They are however generally on the inside of the house. Sun hitting them will cause a temperature rise within the house.

You have the same external air temperature on all sides of the house? Fascinating, but unlikely this far away from the equator.

The air in that space is generally connected to the air in the rest of the room, whether the curtains are insulated or not. Do you have some particular arrangement of curtains where this is not the case? If so, what is it?

Reply to
David Hansen

On Mon, 09 Jul 2007 08:41:51 -0700 someone who may be snipped-for-privacy@care2.com wrote this:-

Incorrect.

It goes down because there is not a solar gain at night. The flow of heat in the fabric reverses. Ventilation will reduce the temperature of the fabric to some extent, but the extent of this depends on the conditions (including how much heat is being given off by the ground).

Of course what happens depends to a large extent on the particular sort of building one is considering.

Reply to
David Hansen

During late afternoon and evening when the interior gets warmer than outside, any convection through open windows will be from the lower floor up to the upper floor.

So when there is no breeze, especially at night, the upper floor rooms will feel stuffy as air is heated on it's way up, and then flows _out_ of the upper floor bedroom windows when it's at it's warmest.

If you have a spare room/study try and have a large fan blowing air out of that window in the evening and at night. This will help to draw cool night air _in_ though the upper floor bedroom windows when it will be at it's coolest.

If this works out OK then try moving your bed under the window for summer.

cheers, Pete.

Reply to
Pete C

I think it was sol-air, but that doesn't include any time delay functions. The relevant books are in my loft, I think.

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for Solair produced, amongst other things, a link to the Solair "family oriented nudist resort and campground, owned and operated by its members. ..." I don't think that was it.

The gist of it is that the walls and floor slabs act as storage heaters, soaking up heat in the sunshine and re-emitting it from both wall faces, some time later. This sounds a bit extreme for that to fully explain it. Have you ensured the heating is OFF, isolated with working valves. Is it UFH?

Reply to
Aidan

at low level to get the maximum

Thats a good trick..

Reply to
The Natural Philosopher

Single glazed windows, and floor length interlined (3 layer) curtains: There is almost no air movement between the trapped space and the room.

The curtains/sg windows are in fact more effective than triple glazing.

Reply to
The Natural Philosopher

That radiates straight out. The ground surface is typically the coldest place at night - hence ground frost/mists etc.

Openimng low level windows is very effectice in intridiceing cold air and if teh upper windos are open too, a chimeny effect develops.

Reply to
The Natural Philosopher

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