New build not performing as expected... Advice needed « Alternative Technology Assn Forums

Alternative Technology Assn Forums » Sustainable Building

New build not performing as expected... Advice needed

(15 posts) (8 voices)

Started 8 years ago by MissPanz
Latest reply from Eamon

Tags:

MissPanz
Member

Hello,
We are finishing off a build on the Fleurieu peninsula in SA, the usual story, had to move in before it's quite finished.

Now I know we are having a heatwave and all but the house is really not performing as I'd like, it's getting really hot,so that even when the house cools down the furniture is hot!!!

There are a couple of things that I know are making it hot, and this is because the build isn't complete, there's no shading on the north facing front and there is a lot of glass there so I know this is acting like a radiator plus there is no western shading on those two windows yet ( i know everyone is now shaking their heads sadly at our folly ).

I know that these fixed shades should be there but there's a long story behind this all....

The thing is that although the back part of the house is cooler, ( house is about 7m deep) and the air circulation is good, even in the back of the house all the internal wall linings are hot at the middle of a hot day. There's a section where the internal lining is off and I've checked the external wall construction/ insulation and I want to know if the architect has f***** up almightily as the wall is this, colourbond outside, then foam/foil insulation with foil facing inwards, then batts in the wall cavity .

So my questions are:

Would the lack of shading make the house that hot so that internal linings (walls) heat up to that extent?

How deep should our north and west fixed shading be, the plan says 900mmm? Is is different for west shading ? Windows are double glazed

And has the architect stuffed up with wall insualtion with the result that the back walls,in the cooler part of the house are heating up or is that the sole result of the radiant heat via the unshaded windows ???

Any advice appreciated

Posted Thursday 16 Jan 2014 @ 9:10:02 am from IP #
Bushwalker
Member

Hi MissPanz,

Shade the N + W windows and walls would be my first advice. Use anything you can reasonably lay your hands on as a temporary measure. Is the glazing low-e, that might help but the best bet is to get the sun off the glass.

Re the internal walls being warm to touch, we have had several days into the high 30's and 40's. The heat will slowly penetrate the building, especially if it has unshaded areas that should be shaded, and if the building is not sealed. If the insulation is inadequate, that won't be helping either, but the question is, is it performing to the design?

Monitor the outside temperature, and if it falls below the internal temps, then open windows and let cross ventilation occur to take out heat.

I'm gathering you do not have any cooling?

Re the wall and the foam/foil insulation. Check, this might be foil on both sides, but in any case, the important part of the foil works both ways. On the outside it reflects radiant heat, on the inside it has low emittance, restricting radiation of heat into the building - the difference in effectiveness is very low.

Something also worth looking at is sealing. If there are areas that are not complete, you likely have a lot of air infiltration. This will work against the design of the house until the building envelope is completed.

Finally, you will be pressed to find a house in SA without AC that is not warm at this stage in the heat wave, and plenty with AC that are also quite warm. Insulation is basically a time sink for heat and it can be swamped if the heat does not dissipate through cool nights etc. You need a very strong design, lots of insulation and substantial internal thermal mass to weather out a heatwave and remain cool.

Ask your architect to visit with his IR thermometer or camera to check the place out.

Hope that helps,

BW

Posted Thursday 16 Jan 2014 @ 1:07:55 pm from IP #
tom
Member

See my long winded post here: http://www.ata.org.au/forums/topic/12311. Low-e glass does not let heat out, so once heat gets in, it's stuck if the outside temperature is too hot to open windows. Put external blinds up ASAP. It worked for me.

Posted Thursday 16 Jan 2014 @ 8:51:02 pm from IP #
Liliana
Member

We are also in the position of living in an unfinished house and trying to varnish in the Melbourne heat this week so the house is not completely sealed as our east-facing windows are in the garage. As a temporary measure we found Renshade on our west facing glass (which is already double-glazed and low-E) made a noticeable difference to the room. Yesterday evening it was the coolest room in the house and actually quite liveable! Our north-facing rooms were the hottest and - yes - even the furniture was hot. So I can only agree with everything said so far. Seal as much as you can, shade east and west and only open the house when it is cooler outside.

Posted Thursday 16 Jan 2014 @ 9:00:31 pm from IP #
Benny
Member

MissPanz - its hard to give definitive advice when your descriptions are somewhat subjective. If you can get some real thermometer measurements and especially wall/ceiling measurements with an IR thermometer or camera it would be even better.
Re N facing "shading" - if you mean eaves then 900mm should be OK as a rough guide. If you want to measure it yourself go out there at mid-day, hold a stick horizontally out from the wall above the windows and ensure the shade from the stick extends all the way to the ground and away from the wall a short distance. The shade should completely cover the windows from about Dec to March - or whatever you regard as the hot season.
Eaves are no good at all on E and W walls. Repeat the above in the morning and afternoon and you will see the 900mm eaves will barely shade the windows/walls. You need some form of vertical shading device outside those walls/windows.
Your wall constructions sounds OK - don't panic if the foil is facing inwards - but the most important factor is whether the foil faces an airgap. If its hard up against the batts its doing nothing. Also you say there are batts/foam but what is the R value of these ?
If your internal air is getting hot (and circulating well) then it will heat everything up from inside of course. I have been to houses where its very hard to use my infra-red camera to assess heat penetration because the clients leave all the doors open and let in the "fresh" but 30C air and heat the ceiling/walls up from the inside. Are the internal wall surfaces warmer than the internal air ? If so then the heat is coming in through the wall. If not they are being heated from the inside.
Can you put temporary shade over the N E and W windows ? Just connecting shade cloth(90%) to the gutter with bulldog clips hanging vertically and pegging/securing with bricks to the ground is a good way to assess how much heat is getting in there.

Posted Friday 17 Jan 2014 @ 12:22:50 am from IP #
alfresco24
Member

"there's no shading on the north facing front and there is a lot of glass there so I know this is acting like a radiator"
That's right - any direct sunlight falling on the glass is providing 800-1100 Watts/Sqm energy, even when the sun is at a high angle the Infrared & thermal conducted energy coming off the glass is IR re-radiated and is very high, and likewise reflected heat (IR) off pavement outside the window is also coming in. Put pot plants in front of the outside glass and try to shade pavement at least 2mt out. Having reflective blockout curtains will also help greatly.

"plus there is no western shading on those two windows yet"
Same as above. (Yes we're shaking heads and pointing fingers)

Remember it's not the visible light making the heat, it's the Infrared light energy that comes with it is the culprit.

"The thing is that although the back part of the house is cooler, ( house is about 7m deep) and the air circulation is good, even in the back of the house all the internal wall linings are hot at the middle of a hot day."
A 7m depth is really not much at all and considering all the glass you appear to have it's no surprise to hear what you say. Conducted heat via the ceiling/roof, internal and external walls, and floor will fill the rooms with heat quickly, and that heat will be absorbed by every surface.

"the wall is this, colourbond outside, then foam/foil insulation with foil facing inwards, then batts in the wall cavity."
Benny & Buskwalker have answered most of this. Obviously we'd like to know how thick the batts are and what rating it is. Air gap's are essential and if the architect+builder hasnt included them well that's just ignorance.

"Would the lack of shading make the house that hot so that internal linings (walls) heat up to that extent?"
Short answer - Yes. With 800-1100W/sqm falling on them you can work out for yourself that there's a hell of a lot of energy the insulation has to deal with. Insulation only slows down heat transfer so if the heatwave is long enough eventually everything will get hot, or cold, as the case may be in winter.

"How deep should our north and west fixed shading be, the plan says 900mmm? Is is different for west shading ? Windows are double glazed"
Double glazing only reduces IR coming in, but adding Low-e glass does help reduce the re-radiation into the room. Double glazing is most effective in winter. Low-e glass is marginally helpful in winter. Between a rock and a hard place stuff unfortunately. Curtains are king.

"And has the architect stuffed up with wall insualtion"
Probably not, but the trades people could easily have ruined a good plan by poor attention to air gaps between cladding, insulation and surfaces. The house design has to cater for both summer and winter after all, and when a design is 'rated' it takes into account the whole year data. Therefore you might have AC dependent summer performance but great winter efficiency.

Posted Friday 17 Jan 2014 @ 5:28:54 am from IP #
Benny
Member

I don't want to hijack the thread with a tech discussion but I don't agree with your statement alfresco "Remember it's not the visible light making the heat, it's the Infrared light energy that comes with it is the culprit." Visible light is energy just like IR. If 200W of visible light hits a surface it will get just as hot as if 200W of IR hits it. If you look at the solar power spectrum you will see that the peak is in the visible band, ie most of the energy coming through a window is in the visible range, not IR. Especially when you consider that glass is opaque/reflective to IR but completely transparent to visible.
Double glazing barely reduces radiant heat - IR or visible - over a single sheet of glass. It reduces conducted heat.

Posted Saturday 18 Jan 2014 @ 1:42:20 am from IP #
alfresco24
Member

Benny - afraid not that simple.
Full spectrum sunlight is loaded with thermal energy concentrated in the IR spectrum more than an order of magnitude above the visible component.
It can be demonstrated empirically with a normal downlight and a LED downlight

Posted Saturday 18 Jan 2014 @ 11:54:03 am from IP #
Benny
Member

At this site you can see a solar spectral plot.
http://en.wikipedia.org/wiki/Sunlight
What is "thermal energy" ? Any radiation - it doesn't matter what wavelength - when it is absorbed by a surface will be changed to heat/thermal energy. It doesn't have to be infra red to make heat. Look at the chart - it shows there is more energy in the visible band than in infra red. Plus as I said, glass blocks much of the infra red - from outside solar radiation as well as inside - the greenhouse effect works both ways.
Apologies again for hijacking the thread - I won't comment further.

Posted Sunday 19 Jan 2014 @ 10:55:57 am from IP #
alfresco24
Member

Benny, I'm glad you referenced that, still not the complete/right answer tho.
There are two parts to understand, what the sun does and what our surfaces do.
Yes - all wavelengths will heat a surface but to varying degrees.
The sun's raw power is stronger in the IR region calculated as a function of wavelength using "Planck's black body equation." http://en.wikipedia.org/wiki/Planck's_law
and http://en.wikipedia.org/wiki/Thermal_radiation
Note: Not to be taken too literally with the basic meaning of 'colour temperature'.
You also have to take into account that higher wavelengths visible to UV get scattered more by the atmosphere, whereas more IR will get through the atmosphere to our surfaces.
You'll find that the shorter wavelengths to UV get absorbed very close to the surface of a material, whereas IR penetrates deeper. Therefore material heating depends on its spectral response, thickness, and thermal conductivity.
As an extreme example if the material is thinner than the wavelength of IR then Visible to UV would win hands down. So it depends on exact design considerations but in our terrestrial real world we dont build with materials that thin.
IR gives us more heating because our materials (absorbers) exploit that, simply because that's what the sun gives off the most.
(credit to Prof X at UoA for assistance explaining this simply)

Posted Monday 20 Jan 2014 @ 12:59:44 pm from IP #
Greg C
Member

Don't worry about the scientific explanation, the reason the house is heating up is because the sun is getting in when it is not supposed to. Same thing happened when I replaced the pergola slats a few years ago at our house. Everything should be OK as long the pergola is designed and built properly

Posted Tuesday 21 Jan 2014 @ 7:34:30 am from IP #
Eamon
Member

MisspanZ, try observe how long the heat stays in the house and on the walls. With colorbond, yes you will have intense heat transmission internally with/without a gap, if the gaps are blocked they negate the use as was previously said. If this heat is rising straight to the roof area and this is not evacuated, you will be sitting directly beneath an oven.

Posted Tuesday 21 Jan 2014 @ 1:44:56 pm from IP #
MissPanz
Member

Hello , thanks for the advice, we got blinds and renshade and it helped a lot. The reason we don't have north or west shading is because the build is incomplete, we' re not quite so naive as to not have it at all.
The advantage we have is we are on the Fleurieu and quite high up so we get cool changes and it is always cooler here than Adelaide.
The wall batts are an r4 value wool batt and at least 50mm thick, so I think that should be ok, I have to look again and sort out the air gap.
We have unfortunately had probs with the buillder, it's hard to project manage when people actively lie to you....

Posted Tuesday 4 Mar 2014 @ 11:13:50 am from IP #
MissPanz
Member

Eamon, not quite sure what you mean by ' You will have intense heat transmission ...with/without a gap' , do you mean that having an air gap makes no difference to the heat transmission?

Posted Tuesday 4 Mar 2014 @ 11:54:15 am from IP #
Eamon
Member

MissPanz said:
Eamon, not quite sure what you mean by ' You will have intense heat transmission ...with/without a gap' , do you mean that having an air gap makes no difference to the heat transmission?

Sorry, I meant to say cavity. If there is a cavity between the batts and the colour bond, this heat will rise up. If there is no gap except for between the batts and gyproc, then the heat will accumulate only against the batts and not inherently rise. Additional cavity is always good when considering thermal transmission hot or cold.
By the way if you had an adjustable shed or external sliding louvre shade, you could attain cool shading in the summer and open up to allow heat in during winter.

Posted Tuesday 4 Mar 2014 @ 2:21:01 pm from IP #

RSS feed for this topic