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Raising a house's EER to 7 or 8

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Started 1 year ago by gav3500
Latest reply from dave lawrence

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gav3500
Member

My family is planning an extension in Canberra to a 1970 brick veneer, wooden floor house. The old house faces ENE with most windows on that side and most of the rest on the WNW side. The SSW wall is well shaded with a hedge and the NNE wall has a carport against it. Floor area is 110sqm. It was about EER 1.5 (or less) when we moved in five years ago. Since then we've had wall insulation pumped into the walls. The existing house had roughly R3.5 in the ceiling, though it is a little patchy. The house is cold winter and cool in the mornings in summer.

To qualify for a MECU green loan we'll need to get the EER value one higher than that required by the Government. Mid next year the government will require EER6 so the house plus extension will need to hit EER7 or 8. I am encouraged by the zero emission house (http://www.auszeh.org.au/demo.html) which has EER8 without anything really special being done to it. The best plan for the extension is about 70sqm with roughly 2:1 aspect within 5deg of north.

I reckon I can come up with a solar passive design for the extension, plus solar hot water and 3-4kW of power generation, but will it be enough to pull the whole package up to EER7-8?

We are currently considering for the old house:
- double glazing (possible tinting the windows also).
- improved door sealing
- fixing the ceiling insulation
- subfloor insulation

Other possibilities include:
- Reroof (in steel) and sarking (alternatively I could staple sarking on the inside of the roof beams).
- Increasing the ceiling insulation. It's a cut roof. Perhaps putting plywood down on top of the ceiling joist (creating a trafficable surface) which would allow a fairly seamless loft of insulation on top. Could even put additional reflective foil under the plywood.
- Ducting hot air from the extension.

The extension could have 15-20sqm of north glass which is overkill for 70sqm. This raises the question as to whether this excess heat can be reasonable ducted to the old house?

Also for the extension anyone has any experience for the durations of full shade and full sun in eave design? I've done calculations for 6weeks either side of the solstices but really I'm only guessing. The calculations are easy enough I just need to settle on the durations.

Finally the wife has shown a preference for significant areas of wooden floors in the extension (sigh). Speaking with Dave Lawrence here suggests a raised wooden floor could duct hot air from the ceiling to "bring in" the slab under the floor. The trouble is I have no real evidence it would work, not be too noisy and not consume too much power.

I know there is a lot of stuff here pick off which bits you want. I try and get some pictures together.

Posted Wednesday 25 Aug 2010 @ 3:19:32 am from IP #
dymonite69
Member

I am not sure how EER correlates with AccuRate star ratings.

My thoughts (most cost-effective to least)

1) Weatherseal thoroughly - not only doors and windows but ducts as well, between gaps in floor boards and the bottom plate
2) Top up ceiling insulation
3) Foil lined insulation blanket under the roof (if you wish to live in the loft) - if you put insulation between ceiling joints then plywood over then you will squash the insulation and the effect is lost
4) Appropriate shading to windows during summer
5) Subfloor insulation - it is controversial which is most cost-effective. There is an argument is that you just need to provide a air barrier and that insulation blanket is overkill.
6) Insulating window covering to windows +/- double glazing

Don't overglaze the extension. It will be too hot during the day and too cold at night. It will act as a glasshouse rather than a living space. Getting heat from the extension to the house is not that efficient. It is much better to let natural sunlight fall directly into the old building. You may consider strategically adding skylights but be careful of overheating in summer.

Posted Wednesday 25 Aug 2010 @ 5:25:34 am from IP #
Buzzman
Member

gav3500
What do you mean by "a cut roof"??? Is it a hip roof? Gable ended/ridged? Single plane skillion/flat roof? (Unlikely based on your comments but....)

Without that info......I concur with dymo.

You said 'other possibilities include re-roofing in steel'. Why? What is the current roof? Tiles I assume?

If so, why not just paint them with a reflective paint. Much cheaper than replacement. But do tack foilboard or sarking to the underside of the rafters as well.

If the glazing area can't be avoided, then you will need to:
a) go double-glazed (and argon-filled is best)
b) use external roller blinds in summer AND
c) utilise heavy lined drapes with full pelmet to keep heat in in winter.

And if glass area can be reduced, still do the above. The latter options are cheaper than double-glazing, but D/G is cheaper in new work (the future extension) than retrofitting to existing.....

You pays your money.....

Posted Wednesday 25 Aug 2010 @ 6:27:26 am from IP #
gav3500
Member

Buzzman, a cut roof is a roof made without trusses. The members are individually cut and pieced together. In this case it means many of the internal walls are load bearing.

Current roof is concrete tiles with no sarking. Reflective paint is not allowed on ACT roof. Any colour other than white or off-white. Existing windows are steel framed and reasonable durable (though all the winder mechanisms need replacing). Windows currently have a variety of celluar blinds, holland blinds and heavy curtains, all with pelmets.

D/G is $1-2K per window, cheap enough to consider.

Dynamite, I was considering removing the insulation from the ceiling, putting the plywood down and putting the insulation on top. That would avoid the problem of insulation covering the ceiling joist making it hard to get around in the ceiling. Roof isn't tall enough for a loft "room".

Posted Wednesday 25 Aug 2010 @ 7:00:11 am from IP #
dymonite69
Member

Gav3500 said " putting the plywood down and putting the insulation on top."

It would reduce thermal bridging from exposed joists but then you end up stepping and squashing the insulation.

Posted Wednesday 25 Aug 2010 @ 10:29:00 am from IP #
Catopsilia
Member

gav3500
Re: "full shade and full sun in eave design"

Designing to let sun in up to the date of the equinox makes most sense. In fact, the sun is moving north or south so fast at that time of year that changing the angles doesn't make a lot of difference. On the summer side of the equinox, the morning and afternoon sun do not shine in through a north-facing window anyway. On the winter side of the equinox, morning and afternoon sun penetrate right to the back of the room.
I now favour not bothering about shading with the eaves, but putting solar pergolas above the windows. Nothing fancy or adjustable or automatic, just wooden slats angled to let sun through only when the sun angle is low.

Posted Wednesday 25 Aug 2010 @ 2:14:36 pm from IP #
dymonite69
Member

Working out when you need shade and sun depends on both the instantaneous ambient air temperature and degree of sunshine.

My experience is that below around 15 degrees inside you can well do with full sun the whole day. When the temperature is above 22 then you it is comfortable in full shade. For anything in between it varies.

Passive solar largely deals with averages. Slight changes in district can alter these variables. And on any given day you could deal with full cloud or full sun with not much difference in outdoor temperature.

Fixed shading tends to restrict the flexibility in controlling heat load.

Fixed eaves do not provide full shade or full sun but different (but predictable) proportions as the day progresses.

Horizontal eaves tend to shade the top of windows during winter.

Uptilt eaves effective raise the actual head height of the eave to prevent this problem.

Solar pergolas achieve a similar effect as the bars of light shrink and expand in size.

I think the best solution is if you actively control the solar gain on a daily basis with adjustable shades (and have no eaves).

Posted Wednesday 25 Aug 2010 @ 2:48:32 pm from IP #
Catopsilia
Member

The simple solar pergolas I suggest need not be very wide. A few weeks on the winter side of the equinox their shade affects only a narrow strip far into the room, if they make any shade at all.
A well known small demonstration house built in north Canberra about 1995 had a narrow fixed solar pergola instead of northern eaves.

dymonite69 advises: "actively control the solar gain on a daily basis"
I am very happy that my house remains comfortable through nearly every day with its controls adjusted only twice a year. Perhaps my climate (NW Slopes NSW) is particularly favourable for this strategy.

Posted Wednesday 25 Aug 2010 @ 10:54:19 pm from IP #
dave lawrence
Member

eaves have other functions too , besides sun control (admittedly very important)

Posted Wednesday 25 Aug 2010 @ 10:57:17 pm from IP #
dymonite69
Member

Where we are we get 50% less solar insolation in winter than your district. The weather bureau says that we get 1 in 3 days of sun. It seems less than that. It is about once every 1-2 weeks where we can open the blinds and actually feel the sun's warmth. Mid Autumn already gets cold and isn't unitl mid Spring that air temperatures are comfortable agian.

So it ends up being an either/or situation. Most of the time our windows end up being a liability rather than a gain.

If I end up building in this area again. I would use smaller windows and have the flexibility to get sun in during the shoulder months.

Posted Thursday 26 Aug 2010 @ 12:55:35 am from IP #
gav3500
Member

My previous house had no eaves (and no shading). When it rained hard the gutters would overflow and water would roll down glass. That plus the constant sun exposure rotted out the timber windows in no time.

Your home suggests a 6:1 thermal mass area to window area ratio so I'll work on that.

I'm not sold on solar louvres. At any angle other that the set one they shade, though the light bleed may not make it obvious.

Currently the heater goes on sometime in April and off sometime in October. Equinoxes are in March/September. Thermal mass will have a seasonal lag as well as a diurnal lag. Atmospheric damping lag is about 6 weeks, guess the same for thermal mass. The discussion is around full sun and until the summer shading there will be at least partial sun. On the flip side October and March can be hot. Daytime temperatures are normally good from October through to early May.

My first guess was full sun from early May to early August and full shade from early November to early February. Equinoxes for sun are probably ok. Would need to restrict window height.

I've dropped an initial floorplan of the extension here:

https://sites.google.com/site/gavspace/house-extension

The extension comprises (from west to east) living area, kitchen and dining with a new laundry tucked in the south side. North follows the orange line.

Posted Friday 27 Aug 2010 @ 6:43:50 am from IP #
dymonite69
Member

Uptilt eaves are a good idea to maximise solar gain to the top of the window in winter but still provide shade in summer. Alternatively have a shorter eave to provide rain protection but then attach adjustable shades to provide flexibility, This can provide complete shading if it gets hot in mid Autumn/Spring.

Will your existing house shade the extension. What is the distance between the two? Having higher set windows will help reduce unnecessary shading.

Posted Friday 27 Aug 2010 @ 11:46:46 am from IP #
petacat
Member

My house is in Canberra and it is very clear to me that allowing as much sun as possible in during Winter Autumn and Spring months close to Winter is the most important part of the design. Eaves of about 400-600 mm on the north and 3-400 mm above the window sill top works well. The CSIRO publishes books which allow you to calculate the perfect sizes.

You really want to block the sun out from late October through to mid April. The rest of the time sunshine is your friend in Canberra. You do not want to block ANY of it coming in to the house.

If you can arrange a solar chimney in the design then you will get the lovely cool night air flowing through on the still Summer nights. I installed a solar panel for "active" heating as well. This is fairly effective but in hindsight I might have been better off double glazing another two rooms (south facing glass in one and North in the other.)

Double glazing is highly effective. Thermal mass is important and so is good insulation. Do not try to go overboard with expensive thermal mass approaches. A good thick slab on the extention and dark tiling will give you most of what you need. Don't skimp on the slab insulation either - especially at the margins of the house.

Just double glazing and the solar chimney arrangement plus simple eaves have reduced my total energy consumption to 23% of what it was before doing that work. I also grew a climbing vine on the large brick wall facing West and that stopped the rooms at that end getting to over 35 degrees in January/February. Last Summer it was a maximum of 26 degrees in those rooms when the outside temperature was 39.

My house faces north and has mostly glass on that side. It is 22 degrees inside without any other heating but the sun right now. It will get to around 25 this afternoon - when I close the curtains, I expect not to use heating until after 8 PM, when I will keep the whole house warm with a small gas "room heater". The dark slate floors keep the heat in so that I comfortably walk with bare feet on the slate in the mornings when outside it is -5 degrees. It is a great pleasure to do that while listening to radio announcers complaining of the cold.

My heater is not used until May unless there is a really cold snap. Last year I had it on for one hour in the morning and occasionally at night in September. It is all because of the clear sunny days and the amount of sun let in to warm the house. Total yearly gas bill for heating, cooking and hot water is $600. For the Winter quarter I had a bill for $90 for electricity (everything else but the gas).

What I am saying here is that you can do an awful lot without spending much. Retrofitting double glazing is not expensive for the benefits. You really notice it in Winter and hot summer days.

Automatic opening and closing curtains work for me because I leave for work at about 7 and arrive home after 6. In mid Winter this means that the curtains open when the fog lifts and close at around 4 PM when the sun is too weak to warm anything. Keeping the warm inside with good curtains is still essential even with double glazing.

As with most things careful planning and design makes all the difference and most of the expensive options are not needed really.

Posted Saturday 28 Aug 2010 @ 4:14:04 am from IP #
Buzzman
Member

I haven't tried this myself, but I read in a DIY mag somewhere about someone who used second-hand Cooper-louvre-type frames, but with fibro 'panes' instead of glass, and mounted them horizontally as an adjustable 'solar pergola'.

Then drilled and threaded a hol through the 'tab' that forms the end fo the lever that opens and closes them, then used threaded brass rod to wind this in and out, utilising off the shelf windo-winders mounted on the support poles of the pergola at waist height.

Wish I could remember where I saw it.....sorry.

Posted Monday 20 Sep 2010 @ 5:15:57 am from IP #
dave lawrence
Member

re : above post ,I have done that myself, and I think it was featured in a permaculture magazine years ago . it is really easy and 6 mm F/c fits nicely into louvre gallerys . We used the gallerys vertically suspended off west facing wall , but yes mounting them horizontally has some advantages . either way is beneficial .

Posted Monday 20 Sep 2010 @ 6:37:17 am from IP #
CunningPlansDept
Member

What's the shading program you've used?

At summer solstice, how much morning and afternoon sun comes into your windows from the south?

Posted Tuesday 21 Sep 2010 @ 10:46:05 am from IP #
dymonite69
Member

You could use this:

http://sunposition.info/sunposition/spc/locations.php

Posted Tuesday 21 Sep 2010 @ 12:43:32 pm from IP #
CunningPlansDept
Member

Thanks Dymo, that's a handy addition to the visualisation tools.
I'm still interested in knowing what programs are out there to show 3D models and shade patterns easily.

Posted Wednesday 22 Sep 2010 @ 10:59:09 am from IP #
dymonite69
Member

Importantly you need to work out for your particular area in which month you would wish to begin shading the windows (usually when temps move above 18 degrees) and when you want the windows permanently shaded (temps above 23 degrees).

Then you can work out the sun angle at that time of the year and the eave length to achieve what you want.

Posted Wednesday 22 Sep 2010 @ 11:14:38 am from IP #
CunningPlansDept
Member

Setting it to 22 Dec shows quite well a thing that I didn't understand until relatively recently: that the sun spends half the day shining from South of East-West, and at quite a low azimuth so bypasses any eaves.

I'm wondering if melbourne hospital's vertical external louvres are adjustable for that?

Posted Wednesday 22 Sep 2010 @ 11:35:50 am from IP #
dymonite69
Member

And that is why you should try to avoid having too many windows on the S, W or E side. If you do you will need vertical shades not horizontal ones.

We don't have more than 5m2 of west windows and < 2m2 of east windows. The west is shaded by rainwater tanks and the east is our garage. The south side has a pergola in front of our largest window with a west facing wall.

Posted Wednesday 22 Sep 2010 @ 11:48:14 am from IP #
gav3500
Member

I have used my own spreadsheet for midday eave calculations. The math is pretty simple.

If we have:

h - Window height
a*h - the height above the window to the eave
b*h - the distance out from the window to the eave
theta - The largest angle you want full sun for
alpha - the smallest angle you want full shade for

then
tan(theta) = a/b
tan(alpha) = (a+1)/b

solving for b:
b = 1/(tan(alpha)-tan(theta))
and for a:
a = b*tan(theta)

Put these into a spreadsheet and you can play around.

The sun angles can be retrieved from:
http://solardat.uoregon.edu/SunChartProgram.html

Once you get a feel for what you want you can see how it works using google sketchup.
Just draw a 3D box with some eaves and you and test how it works at other times of the day and when your building is off true north.
view->animation->settings allows you to set the lat/lon and the orientation
window->shadows lets you play with the time of year/day

It's quite instructive. Especially for off true north. 5 deg off doesn't seem to make much difference but over 10deg is significant.

Posted Friday 1 Oct 2010 @ 2:43:23 am from IP #
gav3500
Member

I have been trying to crunch the numbers from Petacat's post and guessing few things. For eaves 4-600 at 3-400 up and guessing a window of 1200mm high (i.e. half height). I get at best 45 deg full sun limit (400/400 - Full sun from about min April) with a poor summer shade. Or a 68 deg shade limit (full shade from late November to mid February) but some shading in winter.

Also eave shading creates fixed shade/sun symmetrically around the solstices. Temperatures however are not symmetric, tending to lag the sun exposure. So Petacat suggests blocking out sun from late October to mid April. That's roughly 66deg to 45deg sun angle. 45 deg would see sun blocked out from late August to mid April and 66 deg from late Nov to late Feb.

This is no criticism of Petacat, it is just using eaves is a tricky business.

Working through dymonite's suggestion of 18/23. Long term averages for Canberra are
Jan 13.2/28.0 Feb 13.1/27.1 Mar 10.7/24.5 Apr 6.7/20.0 May 3.2/15.6 Jun 1.0/12.3
jul -0.1/11.4 Aug 1.0/13.0 Sep 3.2/16.2 Oct 6.1/19.4 Nov 8.8/22.7 Dec 11.4/26.1
http://www.bom.gov.au/climate/averages/tables/cw_070014.shtml

Suggest full shade from some time in Nov to some time in Mar and full sun from some time in Apr to some time in October, neither of which can be symmetric. Allowing a greater tolerance for temperature we could say Oct to Feb and Apr to Sept and have angles of 66deg (Feb/Oct20) and 50deg (Sept 7/Apr 2).

Punch these back into a 1200 window and we get eaves of 1350mm up and 1140mm out. Much bigger than normal in Canberra. Use a full height window and it's much worse. I can see why some solar passive houses have a massive up-raked veranda to try and hit these sun angles.

Posted Friday 1 Oct 2010 @ 3:31:49 am from IP #
dymonite69
Member

The eave calc is tricky. If you use the Your Technical manual you would have to alter the eave height or head height depending on the total window height. This would make for a very uneven looking facade. The other issue is that significant solar radiation reflects from the ground next to the window back into the house. Ideally you would want to shade the ground immediately in front as well (maybe a couple metres). This would make for a very deep eave that would compromise winter solar gain.

The ideal configuration would to have infinite adjustability from zero shade to deep full shade depending on solar gain.

The key thing is amount of insolation for that time of year rather than actual sun altitude. Full sun even on a zero degree day can overheat a house. No sun even if the temperature is 15 outside is still cold.

Posted Friday 1 Oct 2010 @ 9:45:43 am from IP #
gav3500
Member

I agree Dymonite that a simulation is better than a simple eave calculation. I just stumbled across energyPlus

http://apps1.eere.energy.gov/buildings/energyplus/

which can plug into sketchup and perform thermal simulation. I give it a go and report back.

I like the idea of the Vergola but they don't seem to have a sun tracking option.
http://www.vergolansw.com.au/

These guys do
http://www.colt-tollfab.com.au/products-and-systems/solar-shading/

But it is focused on shading not sun entry and looks only for commercial systems.

I suspect you could automate the vergola using a PV on the blade and a controller. Lot of stuffing around though.

Posted Monday 4 Oct 2010 @ 11:50:03 pm from IP #
Peterws
Member

Gav3500 - I admire your attitude, but from my limited experience of energyplus its not so easy to get meaningful results, it may take weeks - if its a comparison that you are looking for then maybe Ecotect would be easier and I belive you can download a trial program.......best if luck

I have recently started building my 8 star house in Canberra - just poured the slab last week - its north facing, reverse brick veneer, with PVC double glazed windows, R8 ceiling/roof and polished concrete floors.

I calculated the eaves angles using the recommendations in Your Home Manual and then checked it with a 3D model of the building -the full height windows have 900mm and smaller high level windows have 450mm shade device - it looks about right when you run the simulation.

Posted Tuesday 5 Oct 2010 @ 1:25:20 am from IP #
Buzzman
Member

Dunno if I missed the comment, but it appears from pics on the Vergola website they can also be used vertically as sight or shade screens.

Under 'Architectural' tab there's a pic of a hotel porte cochere with vertical Vergola panels.

But no mention of sun-tracking automation that I could see.

Posted Tuesday 5 Oct 2010 @ 1:43:49 am from IP #
Peterws
Member

by the way - I think you will find that the new BCA became effective in the ACT on 1st May 2010 and if the DA was logged with ACTPLA after that date the development needs to meet a 6 star rating

Posted Tuesday 5 Oct 2010 @ 1:45:32 am from IP #
munter
Member

A little off topic but +1 for the MECU loan. We've found them to be a good lot to deal with and have our house and green loan with them.

Posted Tuesday 5 Oct 2010 @ 2:42:41 am from IP #
gav3500
Member

Peterws. Thanks for your input. I find the your home recommendation difficult because "h" is from the bottom of the window to the bottom of the eave and the headroom is 30% of "h". That makes the head room a recursive definition if you only know the height of your window. For standard full height windows your home effectively says:

Window height (wh): 2100
Headroom (h): 900 (wh*0.3/0.7)
Eave (e): 1350 (0.45*h)

Of course that's not the whole story. Windows are typically recessed about 100mm, this recess mean you are never going to get any sun to the top 100mm so we can reduce the effective window height by that and raise the headroom by it. A half round gutter can extend the eave 150mm out and 200mm up. So we effectively get:

Window height (wh): 2000
Headroom (h): 1200 (900+100+200)
Eave (e): 1600 (1350+150+100)

Dropping that into the spreadsheet gives:
Full sun from: 36.9deg (~May 7 - Aug 5)
Full shade from: 63.4 deg (~Oct 14 - Feb 26)

Is that what you are expecting?

Buzzman,
A vertical vergola could be used as sun/shade device on the western side if you can handle the cost.

Posted Thursday 7 Oct 2010 @ 3:29:04 am from IP #

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