Browse Forums Eco Living 1 Jul 31, 2009 10:05 pm I thought I would do some indicative calculations on how long it would take to get your money back on various energy saving building components:
Ceiling insulation 2-3 years Wall insulation 4-5 years Double glazed windows (new build) 9-10 years Double glazed windows (remove existing and replace) 42-43 years late edit (1/8/09 11:34am): recalculation for DG based on R 0.21 U 4.8 showed a payback 21 years new build and 94 years remove and replace) The assumptions are made below with an accompanying commentary. Uninsulated wall R 0.46 (Brick veneer-Gyprock) Insulated wall with additional R2.0 Cost $14.05/m2 Uninsulated Ceiling R 0.39 Insulate ceiling with additional R3.0 Cost $11.94/m2 Single glazed windows R 0.14 $300/m2 Double glazed windows R 4.8 $388/m2 Heating assumptions:** 1) Electrical radiant heating 2) 6 months/year of heating, 8 hours a day 3) Averaged electricity rate = 13c/kWhr (0.6c/kWh off peak, 0.17c/kWhr peak) 4) 10 degree inside-outside temperature difference 5) Temperate climate (Perth, Adelaide, Melbourne, Sydney) Things that would shorten the payback period 1) Higher than average heating patterns (compared to above) 2) Higher electricity rates 3) Cold temperate or alpine climates (e.g. Hobart, Central Victoria, ACT) 4) Lower unit product cost or superior quality product for same cost Things that would lengthen the payback period 1) RCAC, Natural gas (half cost) or wood heating (one fifth cost) 2) Lower than average heating patterns (compared to above) 3) Lower electricity rates 4) Warm temperate climates (e.g. Northern NSW) 5) Higher unit product cost * Prices from Reed Construction Data 2006 (includes labour and materials) ** Calculations based on pure conductive heat losses and optimal installation and performance of products Re: When will it pay for itself - insulation and double glazing 2Jul 31, 2009 10:16 pm I see a tiny little flaw... our power averages 32c/Kw/h not 17. (85% up) We don't use a radiant heater. We don't have double glazing. We don't have Brick veneer-Gyprock Our walls are not insulated. Temp outside is 7 inside is 19, so 12 degree variation(20% diff) Where you are coming from is where you are going to... Re: When will it pay for itself - insulation and double glazing 3Jul 31, 2009 10:17 pm Very nicely done. I suspect double glazing would cost more than an extra $88/m2. Also, double glazed windows would have an R value well below 4.8 (R 0.25 maybe). Demolition August 2009, Construction Started September 2009, Completed December 2010 Re: When will it pay for itself - insulation and double glazing 4Jul 31, 2009 10:32 pm Casa2 Very nicely done. I suspect double glazing would cost more than an extra $88/m2. Also, double glazed windows would have an R value well below 4.8 (R 0.25 maybe). The DG price and rating was based on a bog standard aluminium casement window. DG U values vary from 2.3 to 4.8 but there are also a wide range of prices. Frame type has a larger impact on price than the extra piece of glass! Timber adds 30% Thermal improved 40% UVPC not recorded but I presume higher yet again. Cost effectiveness is dependent on whether the U value reduction with the high performance frames are proportionate to the increase in cost. Re: When will it pay for itself - insulation and double glazing 5Jul 31, 2009 10:51 pm onc_artisan I see a tiny little flaw... our power averages 32c/Kw/h not 17. (85% up) We don't use a radiant heater. We don't have double glazing. We don't have Brick veneer-Gyprock Our walls are not insulated. Temp outside is 7 inside is 19, so 12 degree variation(20% diff) As per my commentary the factors you describe will alter the equation. If you are only using wood heating at $130/tonne you can multiply the pay back period by five. If you are using a free woodlot then the decision will not be a $ cost issue but if you wish to reduce your annual consumption rate. If you aren't using electricity at all to heat then the cost of electricity has no influence. A 20% increase in temperature difference will result in a 20% reduction in payback period Alternative walling systems such as double brick or weatherboard have negligible effect on R values - 0.05 difference at the most. They can be largely ignored in the calculation http://www.energy.sa.gov.au/be_energy_smart/insulation It is different where you already start with a well insulated wall such as strawbale or ICF. The thermal behaviour for log cabins, Hebel or Timbercrete is too complex to model here but suffice to say they are all much more efficient systems than conventional techniques. In other words, they will benefit less from adding wall insulation and the payback will lengthen. In your case (assuming you pay for wood which I know you are not) Wall insulation Payback = 5 years (base case) * 5 x 80% = 20 years Re: When will it pay for itself - insulation and double glazing 6Aug 01, 2009 10:13 am A couple of anomalies in your data Dyno. The cost of a double glazing retro fit does not take into account that perhaps you are changing the windows because -They are either damaged and need to be replaced, - - You are updating the look of the house and intend to replace them anyway - ie the payback period then shortens up. Also the fact that timber framed single glazed can have almost the same u value as double glazed aluminium frames can be brought into the equation. http://werssearch.freehostia.com/tables/werstable.php?Manufacturer=CEDAR And as per Casas note above - The R value will only be changed from around R0.13 to something like R.38 - not R4.8 - which would be damn good double glazed window And the cost of retro fitting insulation to a Brick Veneer / Gyprock wall is more like $35 to $40 per M2 installed. The $14 is the cost to do it at time of construction. But all good numbers to crunch. and then one needs to include the intangible value of - having a much enjoyable home, and if new windows - more attractive - less drafty home- quieter due to the insulated walls and ceiling, and many more intangibles that cannot have an exact $ value put onto them. Steve Re: When will it pay for itself - insulation and double glazing 7Aug 01, 2009 11:59 am Yak_Chat perhaps you are changing the windows because - need to be replaced, - Then payback would be similar to building as new since you are replacing your windows at an additional marginal cost of $88/m2. Yak_Chat And as per Casas note above - The R value will only be changed from around R0.13 to something like R.38 - not R4.8 - which would be damn good double glazed window Sorry this was a typo. It was supposed to be R 0.48 resulting in U 2.1. U .21 is a very good DG assembly and the results obtained reflect this. This may be too generous. Now I did a recalculation for U 4.8 (an entry level DG) which would be more realistic for the indicative costs. The payback is 21 years for new build and 94 years for retrofit. Yak_Chat timber framed single glazed can have almost the same u value as double glazed aluminium frames. You correctly point out that frame type can have a significant effect on whole window R values. Earlier I indicated the marginal costs for more insulating frames e.g timber, thermal improved or uVPC. The increase cost proportionate can be added to the payback period and the improvement in U-values subtracted from the pay back period. e.g. timber frame cost = 130% of base case, U value = 70% of base case Payback period = 21 years x 130% x 70% = 19 years. Yak_Chat And the cost of retro fitting insulation to a Brick Veneer / Gyprock wall is more like $35 to $40 per M2 installed. The $14 is the cost to do it at time of construction. Easy - cost of retrofit is 2.5x the new build cost. Multiply 4-5 yr payback by 2.5. Wall insulation retrofit payback equals 10-12 years. If you have industry costs for ceiling insulation retrofit then I can redo that calculation as well. Yak_Chat and then one needs to include the intangible value of less drafty home If you retrofitted weatherseals to old windows, it might be enough to reduce this impact to acceptable levels. Re: When will it pay for itself - insulation and double glazing 8Aug 01, 2009 12:02 pm Casa2 Very nicely done. I thought it would be a useful exercise to see which intervention has the shortest payback period in relative terms. For a new build: Wall insulation takes twice as long as to pay back as ceiling insulation DG will take 4 times as long again (see revised calculation in later post) Re: When will it pay for itself - insulation and double glazing 9Aug 02, 2009 1:17 pm Interesting Calc. It certainly shows the relativities between the various energy saving measures and you would certainly insulate (and draught seal, zone the house for heating and cooling, implement sun control and correct orientation) before you double glazed. But there are a number of other factors that in my opinion still make DG worth while. Energy Prices are going up and are likely to continue to climb. A doubling of energy prices conservatively within ten years will greatly impact on this simple calculation – decreasing the simple return period quoted. (In my opinion it is likely to go up more than this, considering the Carbon reduction programs and carbon trading.) The value of double glazing in a house does not just magically disappear as soon as it is included in the housing fabric. As an example take the situation of two near identical houses side by side, one with DG the other without. Which one are you more likely to buy? DG house of course. This greater market interest would tend to increase the value of the DG house. Would it increase the value by the increased cost of the DG? I don’t know. But there certainly would be some retained value. And the coming of mandatory energy efficiency disclosure in the housing sector and increased energy costs the value of DG will be reinforced. DG will last the life of the house (hopefully a lot more than 50 years - if it has DG it will encourage the houses longevity - very expensive to retrofit) and is an asset in a house and will increase its resale value. An anyway financial matter should not be your only consideration. What about the embodied energy of the glass and how quickly that will be recovered. According to Prof Bill Lawson (Book - Building Materials Energy and the Environment) glass has an embodied energy of 13 MJ per Kg to process the glass. Add another 50% for window manufacture – so say 20 MJ per Kg. A square metre of 4 mm flat glass would weigh approx 10 kg – so 200 MJ of embodied energy. If I followed d69’s calc (and using those assumptions) 1 sqm of DG will save approx 100 MJ per annum over single glazing. So a return of embodied energy in 2 years. That’s pretty good -much better than PV. Additionally DG adds to thermal comfort of the home. Do you expect a financial return on money spent if you buy a comfortable chair? If you can afford it and have done all the other things (with shorter return periods for money and embodied energy) to increase the thermal performance of your house then consider double glazing. Do it not necessarily for the money but because it is the right thing to do for our environment. Re: When will it pay for itself - insulation and double glazing 10Aug 02, 2009 2:10 pm Eccles you would certainly insulate (and draught seal, zone the house for heating and cooling, implement sun control and correct orientation) before you double glazed. But there are a number of other factors Energy Prices are going up – decreasing the simple return period quoted. greater market interest would tend to increase the value of the DG house. So a return of embodied energy in 2 years. That’s pretty good -much better than PV. Additionally DG adds to thermal comfort of the home. Eccles, all very good points. It goes to show that market price does not always correlate well with energy cost or raw material cost. This skewsthe market, forcing it not to favour DG. Saleability and changes in energy prices are important factors to consider. However, the magnitude of these changes are speculative. One also has to accept the possibility that the financial investment may not be returned in one's lifetime and that the legacy is left for future owners of the house. In Europe we are beginning to see energy efficient homes penalised in resale value. However, market forces are different. Fossil fuels are expensive, nuclear energy still does not sit well with the community, the climate is colder and the population density is high. Double glazes windows make good economical sense, are more popular with a more competitive market and lower prices. In Australia we have abundant coal and gas (and uranium), the winters are not as cold and there are less people to look after. If someone doesn't have DG, they crank up their gas heater a little and fork out a couple more dollars a day on their energy bill to maintain comfort. It will be interesting to see how much the government is willing to intervene in energy policy. The public needs to understand the personal ramifications of their political choices. They want a better health system but aren't willing to take charge of their diet or pay a higher medicare levy. They want their children to have a better eduction but aren't willing to support the schools and teachers who teach them. Finally, they may wish to ratify Kyoto but not willing to forgo their energy guzzling McMansion. The government is well aware that the green vote is only worth something until it hits someone's hip pocket. Re: When will it pay for itself - insulation and double glazing 11Aug 02, 2009 2:24 pm Eccles Additionally DG adds to thermal comfort of the home. Do you expect a financial return on money spent if you buy a comfortable chair? Good analogy, the comfy chair will have to be replaced some time in the future. DG will be saving carbon and dollars from day one, increasing savings during it's life. I too feel the cost of energy will increase, though my expectation is not just a doubling, more like 4-600% over the next 10-15 years, but this is an assumption... we all know : to assume can make an a ss out of u & me. I also agree that making all the efforts to tighten up on loose fitting doors, windows etc will make a huge diff. In my experience thermal mass and the placement is often overlooked or under rated. I must also add that the best orientation is east of due north, this allows easterly sun, and shields more of the westerly sun from your house so NO windows on the west for me. onc Where you are coming from is where you are going to... Re: When will it pay for itself - insulation and double glazing 12Aug 02, 2009 3:51 pm onc_artisan I too feel the cost of energy will increase, though my expectation is not just a doubling, more like 4-600% over the next 10-15 years, but this is an assumption... we all know : to assume can make an a ss out of u & me. The treasury department has tried to do some projections until 2050: see Box 38 http://www.treasury.gov.au/lowpollution ... apter3.asp and Table 1 http://www.treasury.gov.au/lowpollution ... egions.pdf Re: When will it pay for itself - insulation and double glazing 13Aug 02, 2009 5:01 pm dymonite69 Can I ask why you seem to be arguing against double glazing? I see that you put it in your own home. Are you now saying that if you built again you wouldn't use double glazing and would prefer to pocket the additional money to spend on extra energy costs and other discretionary spending - a plasma screen television or overseas trip for example. I also see by your other posts that you have a very detailed knowledge of passive solar design. Is not DG part of this. Has something changed your mind about the benefits of passive solar design? Regards, Eccles Re: When will it pay for itself - insulation and double glazing 14Aug 02, 2009 5:20 pm Eccles dymonite69 Can I ask why you seem to be arguing against double glazing? I see that you put it in your own home. Are you now saying that if you built again you wouldn't use double glazing and would prefer to pocket the additional money to spend on extra energy costs and other discretionary spending - a plasma screen television or overseas trip for example. I also see by your other posts that you have a very detailed knowledge of passive solar design. Is not DG part of this. Has something changed your mind about the benefits of passive solar design? Regards, Eccles For us it was the right thing because we: a) were building a new house b) we maximised our ability to get winter solar gain b) already had maximised on all other strategies to reduce heat loss c) we were moving into a cold temperate locale I don't think it is cost-effective or sufficient if a) you were retrofitting an old house b) you haven't done everything else to reduce heat loss c) you live in a sub-tropical climate I don't think DG should dominate the discussion about energy-efficiency or meeting mandatory 5 stars. A good passive solar design (which is free) does more than double glazing. If you design with poor solar access then you are behind the eight ball already. Prospective new home builders should be aware that DG will not salvage their inadequate planning. Re: When will it pay for itself - insulation and double glazing 15Aug 02, 2009 6:15 pm dymonite69 A good passive solar design (which is free) does more than double glazing. If you design with poor solar access then you are behind the eight ball already. Prospective new home builders should be aware that DG will not salvage their inadequate planning. Good-O. Absolutely agree. Home buyers shouldn't let sales people convince them that simply putting in DG - which is quite expensive - will give them a sustainable home. There is a lot more to it. If budget is limited there is still a lot that can be done which is free or at lower cost. (Simply not using halogen downlight is one of the best things to change - energy gussling and wrecks the ceiling insulation - and standard bayonet fittings will probably be a lower install cost.) Do sustainable things in the order which will give the greatest benefit, to the home buyer financially and to the environment. The only proviso* that I would give to this is that some things are easy to retrofit - no or little financial penalty for later installation compared to construction time. Double glazing is not one of those things - a very expensive retrofit - so this might also be considered if you think that DG may be good to have in the future . *Edit 10.30pm 2/08/09: And the points listed in my earlier post Re: When will it pay for itself - insulation and double glazing 16Aug 02, 2009 7:03 pm Other points: - Additional measures window coverings and shades can have greater impacts on reducing heat transfer. A curtain over a single glazed windows does more to reduce heat loss than double glazing. A correctly sized eave or awning will reduce heat gain more than low-e or reflective windows. It is advantageous if one has the choice of combining both solutions but what if budgetary constraints forced one to choose between one or the other? - Installing high performance glazing still has to be done in an intelligent manner to reap its benefits. I give an extreme example. Imagine I were to design a house with predominant south and west facing windows. On the south face I put in heat-reducing tinted windows with a low-e coating. On the unshaded west side I install double glazing. It would not be hard to imagine this house would be far more uncomfortable than consideration of good passive solar design using only single glazed windows. I wonder how often is the issue of correct house orientation mentioned when an owner either consults a builder or supplier when developing a window schedule. - There is a wide range in DG performance and price. If done as a retrofit e.g. UPVC or thermal composites may result in a payback period that exceeds the likely lifetime of some buildings. Re: When will it pay for itself - insulation and double glazing 17Aug 02, 2009 7:18 pm dymonite69 Other points: - Additional measures window coverings and shades can have greater impacts on reducing heat transfer. A curtain over a single glazed windows does more to reduce heat loss than double glazing. A correctly sized eave or awning will reduce heat gain more than low-e or reflective windows. It is advantageous if one has the choice of combining both solutions but what if budgetary constraints forced one to choose between one or the other? - Installing high performance glazing still has to be done in an intelligent manner to reap its benefits. I give an extreme example. Imagine I were to design a house with predominant south and west facing windows. On the south face I put in heat-reducing tinted windows with a low-e coating. On the unshaded west side I install double glazing. It would not be hard to imagine this house would be far more uncomfortable than consideration of good passive solar design using only single glazed windows. I wonder how often is the issue of correct house orientation mentioned when an owner either consults a builder or supplier when developing a window schedule. - There is a wide range in DG performance and price. If done as a retrofit e.g. UPVC or thermal composites may result in a payback period that exceeds the likely lifetime of some buildings. Dymo lets NOT go there again... You are making some wild accusations and poor analogies in this last post. Lets not focus on the old stuff and move into what is good. Why do you bag things? That baggage you have is a heavy load, let it go Where you are coming from is where you are going to... Re: When will it pay for itself - insulation and double glazing 18Aug 02, 2009 10:59 pm dymonite69 Other points: - Installing high performance glazing still has to be done in an intelligent manner to reap its benefits. I give an extreme example. Imagine I were to design a house with predominant south and west facing windows. On the south face I put in heat-reducing tinted windows with a low-e coating. On the unshaded west side I install double glazing. It would not be hard to imagine this house would be far more uncomfortable than consideration of good passive solar design using only single glazed windows. I wonder how often is the issue of correct house orientation mentioned when an owner either consults a builder or supplier when developing a window schedule. Why wouldn't one place low e glass in southern windows -wouldn't that slow heat loss. In a well designed house it seems a reasonable strategy. Tinting would be useless as sun would rarely strike the south windows. Unless you are saying because of the size of the western windows all the windows need to be designed to shed the afternoon heat gain so the house doesn't overheat. A very poor strategy. I wish the concepts of correct orientation was understood and adopted by more designers, builders and subdivision developers. These people need to lead because it is not practical to expect the most future house owner to have detailed knowledge of the design technicalities associated with passive solar design. Re: When will it pay for itself - insulation and double glazing 19Aug 02, 2009 11:11 pm Eccles Why wouldn't one place low e glass in southern windows -wouldn't that slow heat loss. There are two ways the low-e coating can be configured with double glazing. One reduces solar heat gain and one doesn't. The choice depends on which side of the building you place the windows. Just ordering the same low-e all around (as we initially considered) may not be the optimal solution. Eccles I wish the concepts of correct orientation was understood and adopted by designers, builders and subdivision developers. This is probably the single most important factor that will influence a house's maximum potential to reduce energy requirements. But as you pointed out it is the most neglected. Re: When will it pay for itself - insulation and double glazing 20Aug 02, 2009 11:17 pm Yay Eccles thankyou, a breath of fresh air.. Totally agree If I had my way most west facing walls would be walls not glass. Thick walls with more than enough thermal mass to easily handle the westerly sun without heating up. We have a rammed earth wall 3 mtrs high and 9 mtrs long. It is our saving grace wall, winter and summer and all part in between. onc Where you are coming from is where you are going to... This is one of the reasons I decided to go overseas for my double glazed windows. As the builder indicated, he's worked on many upmarket builds, these were the most well… 13 19262 For your reference Performance Labels: Window assemblies in housing, except timber windows, must be labelled so the label can be seen when it is in situ. For timber… 6 7735 Hi Mofflepop, I would recommend finding a building designer to prepare plans, they should design to your specified budget. The benefit is you can tender the project out… 9 20432 |