I've always known insulation works on the law of diminishing return. 4 inches fibreglass between the rafters in the loft of a bungalow. Last summer whilst getting down a cobweb I realised how warm the ceiling was. I spent money on some Rockwell to top up thickness. It was well worth it, as comfort level is much better and energy usage is less. Your video is good advice.
I can tell you that the sound reduction improvement is another benefit. We just had our home's roof topped up with additional insulation. Not only are warmth comfort levels improved, but so too is the amount of sound reduction from the fan noise (at high speed) of our heat pump air conditioning system. Those large fan blades spin fast at times, causing a significant amount of noise. Before the top up, the sound entering the house was greatly reduced but since the top up, almost imperceivable now. I love the PassiveHaus concept.
Also factor in the cost of heating or cooling equipment. If you can buy a smaller unit when you have better insulation, that decreases the costs. And probably maintenance and replacement of heating cooling units later!
The amount of insulation depends on the climate you live in. I wouldn't have R-30 walls in Texas but I would in Minnesota. We can have a delta of 80-100F between inside and outside temps for 3 months up here.
Climate is one of the factors. As mentioned in the video, there are also other factors such as building size, price of insulation and energy, material type etc.
If you plot insulation R factor versus how many BTUs per sqft/hr loss a wall assembly has, the curve flattens out around a R-12. This represents the beginning of the point of diminishing returns. For high performance homes, this is how much your external insulation should be for the best price/performance ratio. If you are going to commit resources to external insulation, R-12 should be your target. To prevent the interior side of your exterior sheathing from becoming a condensing surface during the heating season, you only want 1/3 of your total wall assembly R value to be external insulation. This lands you at a max combined wall assembly R value of R-36. Most of the time you will be better served upgrading the BTU capacity of your HVAC system than adding additional insulation beyond R-36.
What type of insulation are you referencing? I'm assuming fiberglass, but this is not the only option. R value might be more accurate (though I've heard there are issues with that as well)
For the calculations is important the thermal conductivity of the insulation material. In the video is used insulation material with lambda 0.034 W/(mK) which could be fiberglass, EPS, etc.
Of course if you're designing your house off-grid, then the price of electricity is no longer a factor in your calculations. The balance is now between the cost of the extra insulation, or the extra solar panels to be able to heat your house in winter, or cool it in summer, whichever requires more panels. Considering how much less power I get from my fifteen-year-old solar panels now than I did when they were new, I think the assertion that they need to be replaced every 25 years is probably not far wrong. Fortunately, insulation shouldn't have that ongoing expense.
I appreciate the eggplant emoji for the size comment. Energy efficiency is a very serious subject, and if we don't insert some humour from time to time it can get quite exhausting. Give us the giggles!
Tha aim of the video is to shed light on the importance of insulation thickness and the return on the investment. Walls, roofs and floors usually have different thicknesses indeed but this should be determined based on an energy model of the specific project.
Nice presentation on the basics of insulation optimization. However I think you failed to really address 'future-proofing' adequately. The low probability of high-impact events leads us to undervalue their expected expense. Furthermore there is great uncertainty of how the magnitude of such events is going to change over time. This leads to great difficulty in figuring out a true optimum. However it is really easy to understand that it matters A LOT that you prepare for all reasonable worst case scenarios you could face. For many such scenarios the correct answer is to 'run away' - tornadoes, hurricanes, fires, and floods (and other outlying extremes) are really hard to prepare for. On the other hand we are rapidly learning how to do this stuff, and it tends to be not that hard. Some of these building features may also aid in preparing for less intense disasters - things like extended power outages, other service interruptions, and other more chronic than acute challenges. These challenges can lead to pipes freezing, deferred maintenance, and other expensive impacts that can be mitigated by insulation or other built features. This is a much more complex optimization challenge.
Thank you for your comment, Jim! Indeed you are right, in this video I addressed the best insulation thickness and not The readiness for high-impact events of building. This topic is of course super important and maybe we should cover it in another video. I would be curious to know what do you add to your designs to get them ready for such "worst case scenarios"?
@@AntonDobrevski Hi Anton, I have some thoughts about this, but am under no illusion that my thoughts represent a complete and proper perspective on this question - it will require input from many diverse viewpoints. Since I live in northern Vermont, the insulation-related scenarios of greatest concern to me come from extreme cold combined with service interruptions for basic utilities. One of the key questions in this regard is whether a house has a good, old-fashioned wood stove. If so, the requirement for insulation in emergency situations is reduced. Otherwise my feeling is that the core areas of a house should be able to withstand about 2 days of extreme cold (without electric power) with a very modest drop in temperature (definitions of modest here could vary significantly). Whatever that amount is would probably suffice for avoiding freezing of pipes for at least a week, although this should be checked. This is a very seat-of-the-pants answer, but I have not encountered any scientific- or engineering-based answers to this question. If you do have a wood stove, it would probably still be best to have a house that would not freeze during a week of extreme weather. Maybe that is a starting place? Of course extreme heat is in many ways a much harder question, and I have little to offer there. BTW, thermal mass obviously figures in strongly in this problem area, especially in the case of extreme heat (or - heaven-forbid - wildfire)
Not sure that graph is accurate. The relationship between energy efficiency and initial investment cost is not a straight line. Costs get exponentially higher to achieve the last 10%-20% of efficiency.
In the graph of total cost analysis, this is considered in the energy costs curve as it is not linear. One option is to represent the energy cost (i.e. energy efficiency) linearly in which case the investment costs are not going to be linear - that's what you are referring to. The other option, which is shown in the video, is to represent the investment costs linearly and the energy costs as a curve.
Ehh, don't forget that the amount of new carbon dioxide released into the atmosphere every year is still accelerating. Find the "worst case" forecast for how ambient temperatures are going to change in your region over the next 200 years, double that, and then insulate to make your house habitable in those conditions. The modern building industry likes to assume a 50 year design life, but I don't see a lot of people bulldozing their 50 year old houses to build new. The next buyers might add some insulation, replace the single glazed windows with double glazed, and repaint, but then they go on living in it. A 200 year design life really needs to be our minimum, and for high-quality houses more around 500 years. If you don't think your house will be fit to live in by then, why not, and what can you change to fix that?
Good video! This adds value to a construction company’s client. Back in the last century (early 1980s), I wrote a program on floppy disk that helped decide the most economical building envelope based on cost of material, insulation and energy costs. It worked great. Glad to see that someone has developed this process commercially. Thanks.
I've always known insulation works on the law of diminishing return. 4 inches fibreglass between the rafters in the loft of a bungalow. Last summer whilst getting down a cobweb I realised how warm the ceiling was. I spent money on some Rockwell to top up thickness. It was well worth it, as comfort level is much better and energy usage is less. Your video is good advice.
I can tell you that the sound reduction improvement is another benefit. We just had our home's roof topped up with additional insulation. Not only are warmth comfort levels improved, but so too is the amount of sound reduction from the fan noise (at high speed) of our heat pump air conditioning system. Those large fan blades spin fast at times, causing a significant amount of noise. Before the top up, the sound entering the house was greatly reduced but since the top up, almost imperceivable now. I love the PassiveHaus concept.
Also factor in the cost of heating or cooling equipment. If you can buy a smaller unit when you have better insulation, that decreases the costs. And probably maintenance and replacement of heating cooling units later!
Very good point as well!
The amount of insulation depends on the climate you live in. I wouldn't have R-30 walls in Texas but I would in Minnesota. We can have a delta of 80-100F between inside and outside temps for 3 months up here.
Climate is one of the factors. As mentioned in the video, there are also other factors such as building size, price of insulation and energy, material type etc.
Awesome job on this video
Thank you!
If you plot insulation R factor versus how many BTUs per sqft/hr loss a wall assembly has, the curve flattens out around a R-12. This represents the beginning of the point of diminishing returns. For high performance homes, this is how much your external insulation should be for the best price/performance ratio. If you are going to commit resources to external insulation, R-12 should be your target. To prevent the interior side of your exterior sheathing from becoming a condensing surface during the heating season, you only want 1/3 of your total wall assembly R value to be external insulation. This lands you at a max combined wall assembly R value of R-36. Most of the time you will be better served upgrading the BTU capacity of your HVAC system than adding additional insulation beyond R-36.
What type of insulation are you referencing?
I'm assuming fiberglass, but this is not the only option.
R value might be more accurate (though I've heard there are issues with that as well)
For the calculations is important the thermal conductivity of the insulation material. In the video is used insulation material with lambda 0.034 W/(mK) which could be fiberglass, EPS, etc.
@@AntonDobrevski thank you for the clarification
Of course if you're designing your house off-grid, then the price of electricity is no longer a factor in your calculations. The balance is now between the cost of the extra insulation, or the extra solar panels to be able to heat your house in winter, or cool it in summer, whichever requires more panels.
Considering how much less power I get from my fifteen-year-old solar panels now than I did when they were new, I think the assertion that they need to be replaced every 25 years is probably not far wrong. Fortunately, insulation shouldn't have that ongoing expense.
Good point. Battery cost/maintenance is also a significant cost-factor for off-grid houses.
I appreciate the eggplant emoji for the size comment. Energy efficiency is a very serious subject, and if we don't insert some humour from time to time it can get quite exhausting. Give us the giggles!
Kind of seems as though you aren’t differentiating between walls and ceilings/roof insulation
Tha aim of the video is to shed light on the importance of insulation thickness and the return on the investment. Walls, roofs and floors usually have different thicknesses indeed but this should be determined based on an energy model of the specific project.
Nice presentation on the basics of insulation optimization. However I think you failed to really address 'future-proofing' adequately. The low probability of high-impact events leads us to undervalue their expected expense. Furthermore there is great uncertainty of how the magnitude of such events is going to change over time. This leads to great difficulty in figuring out a true optimum. However it is really easy to understand that it matters A LOT that you prepare for all reasonable worst case scenarios you could face. For many such scenarios the correct answer is to 'run away' - tornadoes, hurricanes, fires, and floods (and other outlying extremes) are really hard to prepare for. On the other hand we are rapidly learning how to do this stuff, and it tends to be not that hard. Some of these building features may also aid in preparing for less intense disasters - things like extended power outages, other service interruptions, and other more chronic than acute challenges. These challenges can lead to pipes freezing, deferred maintenance, and other expensive impacts that can be mitigated by insulation or other built features. This is a much more complex optimization challenge.
Thank you for your comment, Jim! Indeed you are right, in this video I addressed the best insulation thickness and not The readiness for high-impact events of building. This topic is of course super important and maybe we should cover it in another video. I would be curious to know what do you add to your designs to get them ready for such "worst case scenarios"?
@@AntonDobrevski Hi Anton, I have some thoughts about this, but am under no illusion that my thoughts represent a complete and proper perspective on this question - it will require input from many diverse viewpoints. Since I live in northern Vermont, the insulation-related scenarios of greatest concern to me come from extreme cold combined with service interruptions for basic utilities. One of the key questions in this regard is whether a house has a good, old-fashioned wood stove. If so, the requirement for insulation in emergency situations is reduced. Otherwise my feeling is that the core areas of a house should be able to withstand about 2 days of extreme cold (without electric power) with a very modest drop in temperature (definitions of modest here could vary significantly). Whatever that amount is would probably suffice for avoiding freezing of pipes for at least a week, although this should be checked. This is a very seat-of-the-pants answer, but I have not encountered any scientific- or engineering-based answers to this question. If you do have a wood stove, it would probably still be best to have a house that would not freeze during a week of extreme weather. Maybe that is a starting place? Of course extreme heat is in many ways a much harder question, and I have little to offer there.
BTW, thermal mass obviously figures in strongly in this problem area, especially in the case of extreme heat (or - heaven-forbid - wildfire)
Not sure that graph is accurate. The relationship between energy efficiency and initial investment cost is not a straight line. Costs get exponentially higher to achieve the last 10%-20% of efficiency.
In the graph of total cost analysis, this is considered in the energy costs curve as it is not linear.
One option is to represent the energy cost (i.e. energy efficiency) linearly in which case the investment costs are not going to be linear - that's what you are referring to. The other option, which is shown in the video, is to represent the investment costs linearly and the energy costs as a curve.
Ehh, don't forget that the amount of new carbon dioxide released into the atmosphere every year is still accelerating. Find the "worst case" forecast for how ambient temperatures are going to change in your region over the next 200 years, double that, and then insulate to make your house habitable in those conditions.
The modern building industry likes to assume a 50 year design life, but I don't see a lot of people bulldozing their 50 year old houses to build new. The next buyers might add some insulation, replace the single glazed windows with double glazed, and repaint, but then they go on living in it. A 200 year design life really needs to be our minimum, and for high-quality houses more around 500 years. If you don't think your house will be fit to live in by then, why not, and what can you change to fix that?
Great breakdown. Would help to reference r values in future videos 👍🏽
Thank you, Walter! I am happy you enjoyed the video and I'll keep in mind your feedback about the future videos.
Good video! This adds value to a construction company’s client. Back in the last century (early 1980s), I wrote a program on floppy disk that helped decide the most economical building envelope based on cost of material, insulation and energy costs. It worked great. Glad to see that someone has developed this process commercially. Thanks.
@@weldo1948 Thank you, Weldon! I am glad you enjoyed the video.