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Ventilating a 1 1/2 story house.

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Rorschach

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Accuracy and precision are not the same thing.
Do you in some sort of anomalous zone of steady temperature? Everywhere else in the country gets these big shifts - down to 15º in Bradford! You'd need to keep the duvet on!
Like I said, take it up with the MET office or Wundeground, my calculations are the same as theirs.
 

Jacob

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Like I said, take it up with the MET office or Wundeground, my calculations are the same as theirs.
I see where you have got it wrong; you say you "Have a constant average air temperature of 25c"
What counts is the range, not the average. There is nothing to calculate.
 

RichardG

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Let’s see some figures, this is an interesting and important topic which will effect people more and more in the coming years. I’ve tried to draw on the graph in blue an estimated internal house temperature assuming some insulation during the day and some cooling at night but a I suspect most houses will have a bigger gain than loss as shown so the house will get hotter and hotter.

5BD26D7E-F0DA-440D-805D-F03703EFDD57.jpeg


Certainly my workshop does this, graphs over the last week. Unfortunately the Hottest time is late evening when you most want it cool if it were a house.

D5C36626-05AF-4CE8-A524-F0749032C207.jpeg
BAF8CFBA-542F-4909-9A75-AE57FA47885B.jpeg

So I’d have to minimise the daytime gains by insulation and improve the evening cooling, forced ventilation? May give this a go….
 

MarkAW

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Something I've done which has helped a huge amount is stopping the solar gain during the day. I covered the outside windows on the sunny side of the house.

I imagine that's why many dwellings in continental Europe have shutters on the outside.

Shutting the curtains helps, but not as much as covering the outside
 

Cabinetman

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@Jamesc has been talking the most sense up to now in both his contributions.
By the way you other two, if everybody else is like me, I am just skipping what you’re saying it’s really boring listening to you two bickering. (Again)
 

Duncan A

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Jameshow,
Fans running overnight should help you feel cooler even if they don't directly cool the room down.
There are a number of fans with dc motors on the market which have a dozen or speeds to select from, with some of the speeds specifically selected for quiet nighttime running.
There are a selection here: DC Fans
I bought an Ecoair Zephyr 16" direct from Ecoair and it is virtually silent on the lower speeds whilst still providing a useful and cooling flow of air.
Duncan
 

D_W

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If A/C is the ultimate answer, I agree with the split system suggestion. I had one installed when an exterior seasonal room was made permanent (far cheaper than figuring out ducting through concrete and trying to get adequate cooling from the main system - but cheaper because I didn't' use a mainline dealer to install).

Efficiency of the better splits is incredible.

But for folks who say a fan will never work, it's a matter of what you're used to. First 15 years of my life were in PA in the USA and I slept with a fan. Not sleeping well was rare. One fan set back from the window pushing air out (as long as it's not pushing against the prevailing wind direction) and another light low speed (quiet) fan on the person sleeping and comfortable sleep is had.

it gets far hotter in PA than it does there. Not uncommon to have a week or two stretch with dewpoints higher than you see there and temperatures in the 35C range. Before fans, etc, it wasn't uncommon for people to sleep outside on the hottest days.

Once you give in to the A/C, it's hard to give it up, though. Splits are more efficient, but above and beyond that, their efficiency advantage over cheaper stuff goes up as temperatures get more extreme. Mine will make 18-20k btu on a 1kw draw at 90 degrees F, despite being rated slightly lower (the cooling rating is at something like 98F or 100F), and it has to get well below freezing before it starts to get inefficient (from drawing another kw for a pre-heat coil) when used for heating.

The unit cost (mitsubishi) was about $2k total for lines and both parts (outdoor unit and indoor head). The local authorized installer wanted $5500 installed to start (installation takes about 4 hours total - plus you need an electrician to install a whip disconnect here, and either you or the electron guy needs to put in a dedicated breaker at an exact amperage - if something goes wrong with the machine, it has to have a limited breaker size so that if it goes bonkers and starts to draw huge current, the breaker trips).

At any rate, the contractor discouraged me from installing it myself, so I paid his HVAC guy $750, and even that guy was hesitant to install for fear of a territory war with the other con jobber who handles the brand.
 

D_W

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(brother in law got a smaller unit than mine from an authorized installer for a screen porch for $6k not that long after - but he's pretty easy to separate from his money).
 

jimmy_s

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Insulation helps quite a lot actually as does thermal mass. Passive solar design involves quite a lot of factors. Ideally though you want to try and keep the heat out in the first place. Insulation results in a lower U value. The surface temp on a roof for example can get very high so insulation reduces conductive heat transfer. Thermal mass can delay peak of energy transfer into building as solar heat transfer is cyclic so mass can cause internal temp increase to occur much later than it would otherwise. Solar gain through glazing is pretty much instant as radiant energy heats internal surfaces and dissipates into rooms. Curtains etc are not that good as heat is already inside so external shutters etc. are best. Also infiltration - if its warmer outside then try to keep doors shut etc. Night time cooling is a low energy cooling strategy as is passive stack ventilation etc which can all help keep temps down.
 

jimmy_s

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Just read your post Jacob - the thermal mass being on the outer face can still help reduce overheating as the thick stone walls may result in the heat taking for example 5 hours to pass through so if the wall is at its hottest at say 2pm the max temp may not reach the insulation until 7pm at which point heat may also be transferred internally and externally as outside temp could be lower than wall temp. Over time the wall may gradually warm up depending on weather conditions etc so effects vary day on day. Lower thermal mass from position of insulation will improve response time of heating generally but even that is impacted by levels of insulation and plant sizing.
 

Doug B

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Btw any one finding the workshop too hot too?!
Quite the opposite it’s so well insulated I have to put my fleece on when I go in there, this is the only time the GLW will be in the workshop as she pops in to cool down.
 

Rorschach

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We actually had a nice cooling breeze last night thank goodness. I managed to get my office under 27C for the first time in days, it's a positively chilly 26.9! lol
 

Woody2Shoes

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An excellent source of coolth is the ground beneath us. A couple of feet below the surface here, the temperature is 8'ish to 11'ish C all year round.

Besides stopping heat getting inside the building envelope to start with, and minimising the amount of energy required to cool the air within that envelope (with insulation and thermal mass and sun shielding (could be as simple as a verandah) - details like people use in the design of their buildings in really hot countries) e.g.


I think moving air through the ground before bringing it into the house would be better than air conditioning - like this, perhaps:


Of course, the OP doesn't have the luxury of re-designing/re-building their house! Cross-ventilation (both from side-to-side - during the day - and top-to-bottom - at night) and sleeping downstairs are two quick, easy and cost-free solutions.

Don't forget the cooling effects of plants and water too.
 

Jacob

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Just read your post Jacob - the thermal mass being on the outer face can still help reduce overheating as the thick stone walls may result in the heat taking for example 5 hours to pass through so if the wall is at its hottest at say 2pm the max temp may not reach the insulation until 7pm at which point heat may also be transferred internally and externally as outside temp could be lower than wall temp. Over time the wall may gradually warm up depending on weather conditions etc so effects vary day on day. Lower thermal mass from position of insulation will improve response time of heating generally but even that is impacted by levels of insulation and plant sizing.
I think you are saying that the external thermal mass is a buffer and will reduce the extremes of range of temperatures reaching the inside face?
 

Jameshow

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Thanks for the insights.

The snail workshop dust collector worked ok but isn't a long term fix.

How about a fan in the roof hatch and another in the floor under the stairs. That way cool air would be drawn out of the under floor area and drawn up through the building. However this might mean that air isn't drawn out of the bedrooms?

Cheers James
 

Davey44

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Surely there's a less expensive and simpler solution? What about creating a substantial air inlet low down on a downstairs wall, ideally north-facing, then leave your upstairs/bedroom windows open. You'll get a flow of cooler air from downstairs though your bedrooms and out of the windows. We have a 1930s 3 bed detached and have a facility to leave downstairs windows open slightly/locked and have two large windows on the landing and of course in each of the bedrooms. We are seldom too hot at night.
 
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