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Ceiling Insulation

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Started 10 years ago by muchkin
Latest reply from Nathan Sharp

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muchkin
Member

I am considering improving the insulation in my ceiling and have been getting different stories as to the best approach by different contractors. In one part of the house I have cellulose which I assume was put in when the house was originally built (late 1960s). This is fairly uniform, though gets a bit light on towards the eaves. In the extension I have batts (R3.5).

Is there any value in placing batts over batts? e.g. R2s over the existing R3.5s, to theorectically boost the R rating to R5.5 or is this a waste of money?

Is it OK to add say R4s over the existing celulose or am I better off getting rid of the celulose first before putting batts in, or topping the existing celulose up with more celulose? I've heard that it can be difficult to get even.

Does putting R5s in instead of R4s actually really make any difference, or is this just a way for companies to make more money without any real additional benefit to the consumer?

I know that the effectiveness of insulation all comes down to how it is installed, but any comments would be appreciated. We live in Canberra so good insulation is important, but we also don't want to spend money if it is not going to significantly value add. Thanks

Posted Monday 23 May 2011 @ 12:34:44 pm from IP #
Buzzman
Member

Insulation is unlikely to 'add value' except and insofar as it improves your EER. This has been shown to add value in ACT of approx $8K per 'star'.

Adding insulation will always help, but trying to remove old cellulose could be a right pain, and the peorpl who offer a 'pump out' service and vacuum out the old stuff charge a fortune fomr what I've seen and heard.

Just add more insulation on top an dmake sure it is tightly fitted.

Posted Monday 23 May 2011 @ 1:31:47 pm from IP #
muchkin
Member

Thanks Buzzman

Posted Friday 27 May 2011 @ 5:51:09 am from IP #
Benny
Member

A few other posts have commented on the diminishing returns from going from "standard" to "High" R values. Think of it this way:
no insulation, say gyprock with R = 0.2, so U = 5, ie 5W heat flow per sqm per degC difference.
R2.5 insulation. U = 1/2.5 = 0.4W/sqm/degC. So we have reduced the heat flow from 5 to 0.4, or to 8% of what it was, or by 92%.

Install another layer of R2.5 (at same price as first layer) to bring total R to 5. So now U = 1/5 = 0.2 W/sqm/degC. This is half the previous value of 0.4, but whereas the first layer of R2.5 reduced the heat flow by 4.6W/sqm/degC, the second layer has only reduced it by another 0.2 W/sqm/degC.
Or from 8% of uninsulated heat flow to 4%. So for the same price of batts you get only a marginal improvement with the increase from 2.5 to 5.

Posted Friday 27 May 2011 @ 6:36:27 am from IP #
Eco
Member

Benny I hope you are not arguing for R2.5 insulation. The minimum is R4.1 and more if you have a darker roof - http://www.yourhome.gov.au/technical/fs47.html#levels

I also dislike a simplistic use of the diminishing returns to argue against additional insulation. It is not whether the returns have diminished (clearly they have) but whether the amount of benefit that can be gained from the additional insulation is still worthwhile - or is there a better way to gain a similar benefit. By worthwhile benefit I mean total economic, environmental and comfort benefits. Total economic benefit included consideration energy costs over time (including the fact that energy costs are going to rise much quicker than inflation) and also that it may be possible to decrease other capital costs - e.g. double insulation all round (roof walls etc.) may be able to significantly decrease (if not halve) the size of heating and cooling plant. Does the increase in insulation work in terms of payback period of the embodied energy (and greenhouse gases) of the additional insulation. Also a well insulated house is more comfortable than a poorly insulated house (at least in temperate and cold areas) - this is not taken account of in a simple dollar and cents calculation.

Posted Friday 27 May 2011 @ 11:44:50 am from IP #
Benny
Member

No Eco, I'm not advocating anything in my post. Just trying to answer the original posters questions and provide some example calculations so he can do the sums for his situation and see if its "worthwhile" - what ever "worthwhile" may mean to him.
As you say - he may decide that given he already has R3.5, its more worthwhile to spend the money somewhere else to get a better gain (for him, the environment etc) than just increase R to 5.

Posted Sunday 29 May 2011 @ 10:17:22 am from IP #
muchkin
Member

Thanks for all your comments. I've had it confirmed now from the source that the information on the link above is out of date and the R value for Canberra has now been increased to R5.1. It will be good when it is updated, as some contractors out there are not aware of the change in policy, which added to my confusion!

Posted Monday 30 May 2011 @ 6:55:24 am from IP #
Bearamundi
Member

Have you looked at super insulation, ramping up to R10 in the ceiling and R8 in walls? I have done so, at least in the roof and it makes a huge difference. Put those batts over those batts, and aircell on the rafters, it will be the best thing you have done in a long while. The warmth is amazing. I am in Newcastle and the internal temp hovers around 23 degrees, just right. I run a wood heater on low for a couple of hours and there is no temperature gradient as you move away from the fire to the outer reaches of the house. Also, the heat descends from above not sideways from the fire. But it is the amazing feeling of spacious heat. The air space feels absolutely still and invisibly warm. Going from R7 to R10 was huge, I don't know how the pundits come up with diminishing returns below R10.

Posted Monday 30 May 2011 @ 7:50:17 am from IP #
markymark
Member

Hi Bearmundi,

How do you get R8 in the walls with standard size frame widths?

Thanks,

Mark.

Posted Monday 30 May 2011 @ 11:53:52 am from IP #
Bearamundi
Member

Hi Mark,
I do not have R8 in walls because of narrow frames at 90mm, but that is the super insulation ideal. You can google this high level of insulation.
I would have around R3 in walls. I pulled off plaster internal walls to expose weatherboards. I stapled vapour barrier foil onto weatherboard and then slightly squeesed R1.5 batts against that. My intention was to limit convective flow. I then stapled another layer of foil over the batts so that there was a good gap before I re-sheeted with gyprock.
I put an aircell sheet across the main window behind curtains after sunset as window losses are huge. The other windows have some sort of extra covering as well.
I will double stud-width the walls when I do the extension so that I can get R8.
Draughty, cold homes are more of a risk factor to health than smoking is.
Tonight as I walked out of my piano teachers house, she remarked:" It is so warm today, 16 degrees". Her house inside was much lower than that. I smiled and didn't say anything. When I got home my house was 21 degrees. I lit the fire and half an hour later the other end of the house was 22. Now it is 23, just right. It will be around 21 tomorrow morning.
We don't go out alot in the winter because restaurants/friends houses are freezing in comparison.
I'm not big on clothes and just wear shorts all winter inside, but that is too much info and not a good look. You only live once and might as well be warm I reckon.

Posted Tuesday 31 May 2011 @ 10:14:59 am from IP #
oysters
Member

What is the cost of cellulose insulation vs batts such as rockwool? Is there much of a difference? I'm having trouble finding information online about the cost in Aus...Rockwool is easy to cost, but cellulose like Cool and Cosy isn't.

Cheers

Posted Monday 23 Sep 2013 @ 7:15:24 am from IP #
dlvb19
Member

Cellulose will usually be cheaper than batts if professionally installed as the labor is minimal - it gets pumped up with a giant reverse vacuum cleaner. Takes about 1.5 hour to pump 160m^2 to R5.

I was quoted $1300.00 for cellulose and $1250 for supply only of earthwool batts. Think the batt installation would have cost another $400ish as it takes a while.

Get cellulose! Doesn't blow around. Install less prone to error. Almost 100% sustainable. Better insulation as a whole.

Posted Monday 23 Sep 2013 @ 11:18:23 am from IP #
Johnnojack
Member

Cellulose may be cheaper and better than a bad installation of batts. Personally I have had rockwool batts, cellulose, fiberglas batts and some polyester batts. Cellulose is OK if you never ever go into the ceiling. It is messy and horrible IMHO, that said both rockwool and fiberglass are irritating too but at least it stays put. Polyester is lovely and if you are tired you could sleep in it (don't do this in the ceiling). No experience with wool as insulation but having spent lots of time in the shearing shed as a kid I know it is nice.

Posted Monday 23 Sep 2013 @ 12:56:21 pm from IP #
dlvb19
Member

True, cellulose does tend to coat your shoes with a fine fuzz. Horrible? Aren't you a little hot house orchid (he said cheekily).
Also agree that cellulose and polyester are the only insulation types that wont irritate, even earthwool gives me the itch.

Cellulose insulation resists air movement as it provides a seamless layer. See below where a immaculate fiberglass batt installation was 38% less airtight than cellulose installation. Now consider how much worse this could be when an Australian tradie has a go at it!

"
In 1990, the University of Colorado-Denver compared cellulose and fiberglass batting insulation in identical structures during the winter heating season. They found that the house insulated with cellulose insulation was 38% tighter and required 26% less energy.
"

http://www.builditsolar.com/Projects/Conservation/Insulation/Colorado.pdf

This looks like the original report. Not sure if it was ever published or reviewed, but hey, this is not climate science! Nothing controversial or untried about the methods they are using.

I also seem to recall a report indicating that cellulose deals with increased humidity better (R-value decreases slower than glass/rockwool) however cant find it on the net...it must not exist?

This american (warning, vested interest) link contains good summary of benifits:
http://www.rtekinsulation.com/high-energy-bills.htm

Posted Monday 23 Sep 2013 @ 11:07:19 pm from IP #
yabbietol
Member

I also live near Canberra, I am in NSW at 800m and insulation is important. I have R4 installed in my colour bond roof and in a few spots I have laid left over sarking over the top of the fibreglass. I already have complete sarking directly under the colour bond.
Like the first person in this forum I have often wondered if it is worth doing another layer of fibreglass (R4 or R5) or Rock-wool , which I think can be got in continuous roles and is very fire resistant (I live in a bushfire prone area).
I also have had the thought of complete sarking or sarking with air bubbles layer over the fibreglass. My house is steel framed so the existing batts lie between the steel beams (which are of course heat conductive). So any new layer of insulation would cover the existing batts and steel frame. The question is do the knowledgeable people on this forum think there would be a worthwhile gain in comfort and energy savings?
Another point is in a previous house I had blown in wool insulation which worked well, but was loved by rodents. This was a long term ongoing problem, which required frequent baiting. I note fibreglass is still used by rodents, but seems less attractive to pests. In my existing fibreglass insulated roof I have used steel mesh gutter guard and blocked all openings with steel or Al mesh and do not have rodent problems. I would not use blown in wool insulation again due to rodents and as it is loose it tends to move around in the roof.

Posted Tuesday 24 Sep 2013 @ 12:29:52 am from IP #
tom
Member

I say go for it. I have two layers of R6 in the house we just built. House is 253 sqm, and all internal and external walls are insulated with R2.5. Total cost for insulation and labour was around $9K. Batts are Earthwool, which is recycled plastic or fibreglass.

Posted Tuesday 24 Sep 2013 @ 9:43:25 pm from IP #
oysters
Member

Thanks for the useful replies!

dlvb19, $1300 for cellulose to R5 @160m^2 sounds very reasonable! I guess as well that going more than R5 the cost would gradually reduce (per R) as the transport costs and set up time of the team is already taken care of. I'm thinking something crazy like at least R12, plus a foil layer up top under the roofing material (yet to be decided, probably zincalume). Walls will be strawbale.

Posted Wednesday 25 Sep 2013 @ 3:03:54 am from IP #
dlvb19
Member

Nice going Oysters,

Wish I had put at least R10 in ceiling now. Would have been less than 2k i imagine considering substantial portion of cost is travel and labor.

Run some heat loss calcs and think about what an acceptable heat loss is for your house:

http://smythesdalestrawbale.blogspot.com.au/2013/06/heat-diffusion-essence-of-eco-home.html

Most roofing companies install sisalation (reflective foil) as standard as it helps direct condensation out of the building, as well as keeping heat out of the ceiling. If your building in adelaide (a heating climate) you could use a light colored colorbond/zincalume and skip the sisalation. If you use tiles I would recommend the sisalation as the will be a greater chance of water ingress.

Posted Wednesday 25 Sep 2013 @ 3:31:19 am from IP #
oysters
Member

Yeah, Adelaide is a "heating climate", but I've never fully trusted when builders break it down to such simple terms. It gets more than cold enough in winter to need plenty of "heating", but also plenty hot for a few months of the year in a poorly insulated house to have to run A/C. So I'm going to bank on dealing with both issues if I can I figure in the long run its worth it...I want to build the house to last.

I was having a play with some of those heat loss numbers the other day and I basically came to the conclusion that I'd definitely bank on getting as much insulation in as I can afford. It will be a truss roof, so also easy to add more later...buying batts would be easier for that if I deem it necessary.

Is that your blog you linked to? The air exchange bit is really eye-opening...seriously important! I'll definitely factor this into all the construction details as much as possible. Definitely extends the case for a double entry door/airlock/mudroom. I didn't consider it before at all in my calculations.

Is it as straight forward though in the heat loss for say the floor? Heat rises. Also, the deltaT for your floor wouldn't be as high as the outside air temp...it will be lower in winter than summer, but it would be mediated greatly by all that soil mass. At about 3-4m down in the soil profile its roughly the same as the average outside annual air temp for a location. Or is your floor raised? Also, have you factored in passive heat gain from windows? That might also account for some of your heating?

Sorry I'm drifting this thread!

Posted Wednesday 25 Sep 2013 @ 5:10:44 am from IP #
oysters
Member

Had a look at pics in that blog of that house (I'm assuming its yours dlvb19...thanks for sharing).

If you were to build strawbale wall down to ground level, would that help reduce your floor heat loss dramatically? Essentially the airspace would be "sealed" allowing heat exchange with the mass of the soil underneath, thus reducing heat loss? Or am I missing something?

Posted Wednesday 25 Sep 2013 @ 5:25:49 am from IP #
dlvb19
Member

Yes it's my blog. Glad it made sense.

Very true that heat rises, often this is eschewed from simple heat calcs like the ones referenced as the next logical step is full blown computer modelling with NATHERS programs. As far as I have been able to work out, a good rule of thumb is to multiply the ceiling loss by 1.5x and floor loss by 0.5x. All the points you raise are salient and have been considered to varying degrees. Certainly include them in your own calcs. Yes its a raised timber sub floor, bearers, joists and yellow tongue.

Straw Bale at ground level would deteriorate very fast (unless on a slab) due to moisture. I have a paper that looks at various raised subfloor insulative systems and it indicates that a fully enclosed subfloor will increase the R value, but only by a small amount. Depends on terrain type, topography, wind levels and other factors. BCA requires ventilation and a minimum clearance between bearers and soil, they are very strict about this! To prevent timber rot again.

Posted Wednesday 25 Sep 2013 @ 11:35:15 am from IP #
arttt
Member

Im not sure on the merits of going to really high levels of insulation in australia.
A couple of early posts on this thread discussed how 'worthwile' extra insulation is. see the 5th post by Eco.
one way of approaching this is to compare the cost to the cost of heating the space with say a heatpump (offset with green power or other if you like to be equally low carbon - dont forget the embodied energy of the batts).
I had a quick go at the calculations. Ignoring lots of important variables but got enough there to give a rough indication.
https://docs.google.com/spreadsheet/ccc?key=0Ahi1d6yOlpKHdE5tb2lQbE95ZXVobEpHZERZeEtYb1E&usp=sharing

The number of days to payback look reasonable for say R8 at about 13 years until you realise this is 'midwinter' days so probably 4 times that.

I suspect there might be some value in increasing the rvalue enough to avoid buying a heating system.

But all that maths is well and good when it comes to put the batts in the roof the extra cost of a doing it a bit thicker is pretty small so i bumped mine up to R8.

Posted Wednesday 25 Sep 2013 @ 1:36:09 pm from IP #
oysters
Member

But insulation also protects from outside heat, so a calculation that only takes into account winter heating could be a bit misleading. In Adelaide for example, it certainly isn't winter when our power stations are under peak load...its summer when we fire up endless AC units. Even Canberra would chew a fair bit of AC power over the three main months of summer.

Embodied energy is one of the reasons I was interested in cellulose potentially instead of batts, for the ceiling. Usually it comes from recycled product. Anyone have any good links on this?

Walls, I think strawbale is probably one of the best options available for insulation in terms of overall eco-friendliness. We produce so much of it in Australia as waste its not funny, and not just from traditional wheat crops, but also from rice too (probably enough to do just about every new house in Australia from rice straw, from what I've heard). Its essentially a carbon sequestration building mode, that's probably even better overall than using wood in this regard; most "sustainable" forestry takes places on land that could be set aside for native woodland that also has biodiversity value. Straw production takes place on land that is set aside for global food demand...we can't really not produce it if we want to eat. Rammed earth, earthbag etc I think definitely have their place, and can be very eco-friendly, low embodied energy, etc, however, I would only consider this if using "waste" earth from on site or nearby. Eg soil that comes from under the actual house build that would be removed anyway. I don't consider taking soil from elsewhere sustainable. It takes a long time to produce soil and its a precious resource for growing food and native vegetation. Its also not always that insulative (apparently rammed earth can be pretty good) though of course has great thermal mass. Similarly, I don't rate "earthship" style building that highly. Sure, tyres are free and recycled, and the soil should be able to come from the hole, but doing a whole house build like that takes a rediculous amount of people hours to construct. I can't get over the number of "workshops" people run where they get stacks of "trainees" (who sometimes pay...a bit wrong in my books) out to shift dirt and tamp it down for them in their earthship walls. I can see its place for sure for some needs, eg you want a good load bearing wall somewhere in the house, or a really good retaining wall for a sloped site. But going out of your way to have to do it...hmmm.

Sorry, didn't mean to rant! Thanks for the good info...its good to see people doing calcs instead of just winging it. That's why since I discovered this ata forum I've fallen in love with it!

Posted Thursday 26 Sep 2013 @ 2:58:12 am from IP #
oysters
Member

Info found for embodied energy...

http://www.members.optusnet.com.au/fricker/InsulationTypesRatedByEmbodiedEnergyForPerformance_PROVISIONAL_JMF.pdf

Not sure where this person gets there info from, but some figures for embodied insulation energy that could be of some use for calcs.

Based on this (for ceilings), I would say that once you've put in a foil insulation layer(should be the first move, even before any other insulation, simply because of its summer benefit), then you want to use cellulose. @ R4, Cellulose is 14.5MJ/m^2 vs 33.9 for wool and 80.1 for rockwool. That's quite a difference. I don't know too much about rockwool production, though I gather its a mined resource so area impact is relatively small, but I would stay absolutely away from wool insulation. Excluding the embodied energy (and I'm sure that only takes into account the energy of taking the wool off the sheeps back and processing it), wool is one of the worst things you can do for the environment. The amount of destruction caused by sheep in Australia is out of this world just about. I'm sure the embodied energy of wool goes way beyond what a mined resource like rockwool does, once rangeland degradation is taken into account.

Looking more closely at the cellulose figures, for R8 (arttt's number) that equates to about 8kwh of energy per square metre. Arttt's spreadsheet show's a loss of .045kwh/m^2/day, so that's 177 winter days to pay back the embodied energy, which is nothing really. Heck, if you are just thinking about net energy savings, slap in as much cellulose insulation as you can fit. R20 ceilings anyone?

This webpage is also very interesting:

http://earlywarn.blogspot.jp/2010/09/sip-home-embodied-emissions.html

Posted Thursday 26 Sep 2013 @ 3:20:48 am from IP #
arttt
Member

yep im not covering the summer need for insulation but its the same formulas just different temp difference.

fixed a few issues with the spreadsheet
https://docs.google.com/spreadsheet/ccc?key=0Ahi1d6yOlpKHdE5tb2lQbE95ZXVobEpHZERZeEtYb1E&usp=sharing

included some embodied energy calcs

also now does 'payback' calcs in 2 ways
1)payback of adding each R value of insulation to an uninsulated surface - high levels of insulation look pretty good like this
2)payback of adding 1 more R to a particular existing r value - think of it as 'im insulating my roof should i put a bit more in?" - to me this makes adding high levels of insulation less attractive.

2 very different perspectives from the same numbers

If you want to be scientific about it the analysis needs to be redone to a net present value calculation so you can pick the R value beyond which you are economically or CO2e better off investing in solar panels and a heatpump. looking at the numbers in the spreadsheet my guess is the result would be pretty standard R value.

Posted Thursday 26 Sep 2013 @ 11:49:39 am from IP #
oysters
Member

Yeah it looks a lot better if rather than just financial payback, you look at embodied energy payback.

Probably a better way of calculating it would be not on a mid winter day type calc but by using degree days.

Thanks

Posted Friday 27 Sep 2013 @ 2:08:15 am from IP #
arttt
Member

I hadn't found easily accessible degree days values for Australia before -seems the BoM had them all along.
http://www.bom.gov.au/jsp/ncc/climate_averages/degree-days/index.jsp?maptype=1&period=an&product=hdd18#maps
of course this is sensitive to the chosen base temp for the degree days calc.

For my location heating degree days is about 1500 and cooling is 50 so those 'midwinter days payback' values on the spreadsheet divided by 100 give an approximate payback in years using a degree days approach.

Im scratching my head over how different the straight payback v the incremental payback look - I cant see a big error in the logic (but im not ruling it out) but they tell a very different story.

Posted Friday 27 Sep 2013 @ 12:26:52 pm from IP #
oysters
Member

also if you go to degreedays dot com they have a pretty smashing calculator. Uses BOM stations, with also some contributed stations available too.

I agree, divide your "overall payback time # midwinter days) column by 100 and you'll get number of years.

Hmmm... I'm not really sure what you've calcuated in column I is correct, or meaningful.

It should probably just be the difference between cells in column G.

Interestingly, knowing the HDD, the embodied energy for R12 at your location pays back in just under a year. If money isn't an issue, its a no brainer.

I'll have a bit of a crack at setting up a fresh spreadsheet myself, but not today...AFL grand final and I'm arranging a viewing in a lecture theatre here at Uni in Japan for a bunch of internationals

Posted Saturday 28 Sep 2013 @ 3:29:20 am from IP #
oysters
Member

Another way to think about your calculations, is to think of it as an investment over the course of the longetivity of the house/your ownership of it. SO if that number is say 40 years, run your model for each R value out to that length of time and calculate a total cost of house heating. The lower value wins (assuming you are just paying for grid power).

Posted Saturday 28 Sep 2013 @ 3:37:27 am from IP #
dymonite69
Member

An important factor in a passive solar design is whether increasing insulation can shorten the heating season. Most calculations are based on reducing heat loss during active heating.

I doubled my insulation from R 3.5 to R 7 this year. For the next 12 months I should be able to compare heating requirements with my detailed records over the last 4 years.

Posted Saturday 28 Sep 2013 @ 10:41:40 am from IP #

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