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- CommentAuthorralphd
- CommentTimeFeb 5th 2009
Any hot2000 users here besides Paul?
Anyone tried Hot3000 yet? In theory it looks a lot better, but when I tried it a month ago it crashed on me without doing a full model run.
I've found Hot2000 significantly underestimates natural air infiltration rates in winter (eastern Canada).
I've also found it significantly overestimates below-grade foundation heat loss.
Paul has implied Hot2000 can put out reports based on daily calculations (instead of monthly). Anyone know how to do this?
http://canmetenergy-canmetenergie.nrcan-rncan.gc.ca/eng/software_tools/hot3000.html
-Ralph -
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CommentAuthorPaul in Montreal
- CommentTimeFeb 5th 2009
Posted By: ralphdPaul has implied Hot2000 can put out reports based on daily calculations (instead of monthly). Anyone know how to do this?
I didn't imply that - I just said I wrote a hot2000 model for Tony. The daily modeling on Tony's house was done using TAS by Mike George and that can do daily reports.Posted By: ralphdI've also found it significantly overestimates below-grade foundation heat loss.
How did you find this? With 3.5 years of measured consumption I'm finding the hot2000 model I wrote is within +/- 5% of my actual consumption.
Paul. -
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- CommentAuthorralphd
- CommentTimeFeb 5th 2009 edited
Posted By: Paul in Montreal
Posted By: ralphdPaul has implied Hot2000 can put out reports based on daily calculations (instead of monthly). Anyone know how to do this?
I didn't imply that - I just said I wrote a hot2000 model for Tony. The daily modeling on Tony's house was done using TAS by Mike George and that can do daily reports.
OK, sorry I misinterpreted you.Posted By: ralphdI've also found it significantly overestimates below-grade foundation heat loss.
How did you find this? With 3.5 years of measured consumption I'm finding the hot2000 model I wrote is within +/- 5% of my actual consumption.
Paul.
That's pretty much what Brian Bradley said when I brought it up.
After dozens of hours examining Hot2000 and monitoring and inspecting my house I have determined that Hot2000 is broken.
One flaw in Hot2000 I have been asserting is significant underestimation of air infiltration heat losses. Wang et. al confirmed the AIM-2 model underestimates air infiltration, especially wind-driven infiltration. However I have determined that the largest source of error is not in the AIM-2 model itself but in how it is used in Hot2000.
"HOT2000™ uses a bin based method and long term monthly weather files to analyze the performance of the house."
http://www.ibpsa.org/proceedings/BS1997/BS97_P009.pdf
Using monthly average wind speeds instead of hourly data results in a large underestimation of wind-driven air infiltration. This is because wind pressures increase with the square of the wind speed. I downloaded a week of recent hourly weather data to demonstrate how significant this is.
http://spreadsheets.google.com/ccc?key=pvSh_EdjajHvORAkszPudcw
The average wind pressure determined from the hourly wind speeds is 1.33x the wind pressure of the average wind speed. When taking the average over a month (like Hot2000) instead of a week the difference will be even more significant. Since Hot3000 does hourly analysis it can provide significantly better heat loss estimates than Hot2000.
http://canmetenergy-canmetenergie.nrcan-rncan.gc.ca/eng/software_tools/hot3000.html
As demonstrated by the PassivHaus initiative, it is not difficult (or costly) to build airtight (under 0.6ACH@50) houses. A CMHC study (unfortunately I can't find a link to it) indicated a wall assembly with panels glued & nailed to the studs at their edges makes a virtually airtight wall. Using a bead of construction adhesive and acoustical sealant between wall sections and under the bottom plate will make the whole wall airtight.
The reason why whole house heat loss modeling with Hot2K still comes close to measurements can be explained by the underestimation in air infiltration heat loss being offset by overestimation of below-grade foundation heat loss. -
- CommentAuthorcookie
- CommentTimeFeb 5th 2009
So whats hot2000 or hot3000 then? and where can I find it online? -
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CommentAuthorPaul in Montreal
- CommentTimeFeb 5th 2009 edited
The link has been posted here many many times. Otherwise, google is your friend for finding things online:
http://www.google.ca/search?q=hot2000+download
Take the 1st link that comes up.
Paul in Montreal -
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- CommentAuthorralphd
- CommentTimeFeb 5th 2009
Posted By: Paul in Montreal
Posted By: ralphdI've also found it significantly overestimates below-grade foundation heat loss.
How did you find this? [...]
Paul.
Hot 2000 assumes a main floor year-round temperature of 21C for inter-zone heat transfer to the basement.
It assumes R5.7 (RSI 1.0) for the floor (code 2x10-Over). Both these assumptions are wrong.
1) The main floor temperature will be much higher than 21C during the summer months; an average of 23-25C is likely from June to September. Therefore more heat will be transferred in the summer, increasing the average basement slab temperature, and reducing the heat loss in the winter.
2) RSI 1 (R5.7) between the main floor and the basement floor is too low. Perhaps for upward heat movement it is reasonable, but not downward. I have often measured temperature differences of 2-3C between the slab and ceiling in the basement (i.e. slab 17C and ceiling 19-20C). The stratification of the basement air reduces heat movement.
I managed to find a reference to corroborate my assertion that RSI 1 is reasonable for upward heat flow:
http://oak.arch.utas.edu.au/publications/PDF/R-values%20Part%204%20-%20Flooring.pdf
RSI 2 likely approximates the downward heat transfer through 3/4" hardwood flooring, 3/4" subfloor on 2x8 joists and 8' to the concrete slab.
Lastly, it seems BASESIMP does not factor inter-seasonal heat storage under the house slab. My house was under construction during the winter of 2007, and the slab was exposed to freezing temperatures. It was occupied in August of 2007, and the center of my slab averaged 12-13C during the winter of 2008. This winter the temperature at the center of the slab is 15-16C. Next year I expect it to be 17-18C, and stabilize around 18C in subsequent years.
-Ralph -
- CommentAuthorcookie
- CommentTimeFeb 5th 2009
Do you get stratification in air? I read that any air space bigger then 1cm3 would induce convection? sorry if I'm taking rubbish :o) -
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CommentAuthorPaul in Montreal
- CommentTimeFeb 5th 2009 edited
Posted By: ralphdHot 2000 assumes a main floor year-round temperature of 21C for inter-zone heat transfer to the basement.
It assumes R5.7 (RSI 1.0) for the floor (code 2x10-Over). Both these assumptions are wrong.
How does it assume 21C if you can set the main floor temperature? Also, in my model, I put no insulation in the floor model. Are you using hot2xp to enter the data?
Actually, in my case, 21C is pretty accurate as there's little sun landing on the main floor level and I keep the thermostat at around 21C year round
Posted By: ralphdLastly, it seems BASESIMP does not factor inter-seasonal heat storage under the house slab. My house was under construction during the winter of 2007, and the slab was exposed to freezing temperatures. It was occupied in August of 2007, and the center of my slab averaged 12-13C during the winter of 2008. This winter the temperature at the center of the slab is 15-16C. Next year I expect it to be 17-18C, and stabilize around 18C in subsequent years.
This is particularly interesting for Tony's house as he's using the basement slab as an interseaonal store and dumping extra heat into the ground from solar collectors.
Paul in Montreal. -
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- CommentAuthorralphd
- CommentTimeFeb 5th 2009 edited
Posted By: Paul in Montreal
Posted By: ralphdHot 2000 assumes a main floor year-round temperature of 21C for inter-zone heat transfer to the basement.
It assumes R5.7 (RSI 1.0) for the floor (code 2x10-Over). Both these assumptions are wrong.
How does it assume 21C if you can set the main floor temperature? Also, in my model, I put no insulation in the floor model. Are you using hot2xp to enter the data?
Paul in Montreal.
Good point; with the required configuration for Energuide Hot2000 significantly overestimates below-grade foundation heat loss. With heating in the winter set at 21C and AC set to the same in the summer, the overestimate will be less, but still material (due to underestimation of of the floor R-value and leaving out interseasonal heat storage).
-Ralph -
- CommentAuthorralphd
- CommentTimeFeb 5th 2009
Posted By: cookieDo you get stratification in air? I read that any air space bigger then 1cm3 would induce convection? sorry if I'm taking rubbish :o)
Convection works to move heat up, not down. -
- CommentAuthorralphd
- CommentTimeFeb 5th 2009
Posted By: Paul in MontrealThis is particularly interesting for Tony's house as he's using the basement slab as an interseaonal store and dumping extra heat into the ground from solar collectors.
Paul in Montreal.
I just downloaded the Hot2000 report you did from Tony's website. It looks like you made a mistake in the Floors above basement (4501400000); the RSI is 4.22. If the basement ceiling is really insulated that much, the heat from the basement slab storage is going to be very slow warming up the house above.
-Ralph -
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CommentAuthorPaul in Montreal
- CommentTimeFeb 5th 2009
Posted By: ralphdIt looks like you made a mistake in the Floors above basement (4501400000); the RSI is 4.22. If the basement ceiling is really insulated that much, the heat from the basement slab storage is going to be very slow warming up the house above.
No. it was not a mistake, it was precisely because the basement heat storage is not modeled that I wanted to prevent the heat from the mainfloor transferring into the basement and showing up as an extra heat load on the house (which it's not). I also suggested to Tony that he might want to insulate the ceiling there anyway to prevent his house from becoming overheated from heat that escapes his subfloor store (which he "charges" up from solar collectors).
Paul. -
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CommentAuthorfostertom
- CommentTimeFeb 5th 2009
So remind me tony (sorry, I could look for myself) how does heat get retrieved from store. into the house, if not via warming the basement floor, thence basement ceiling, and on up? -
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CommentAuthorfostertom
- CommentTimeFeb 5th 2009
Posted By: ralphd with the required configuration for Energuide Hot2000
versusPosted By: ralphdWith heating in the winter set at 21C and AC set to the same in the summer,
what is the vital difference here? -
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CommentAuthorPaul in Montreal
- CommentTimeFeb 5th 2009
Posted By: fostertomwhat is the vital difference here?
In the summer the floor temperature rises (unless A/C is running) and hence heatloss into the basement increases and hence heatloss from the basement outwards too. I'm not sure what the EnerGuide settings are for hot2000 as the download version doesn't allow running in this mode. It has presets for various "standard" conditions presumably.
Paul in Montreal. -
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- CommentAuthorralphd
- CommentTimeFeb 8th 2009
Can you tell me the input for the below-grade heat loss (I think it uses average annual ground temperature combined with amplitude & phase of the temperature variation). The Hot2000 reports shows basement temps dropping to 14.5C in Jan, so I can infer that the average ground temp is <14.5C.
-Ralph -
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CommentAuthorPaul in Montreal
- CommentTimeFeb 9th 2009
Posted By: ralphdThe Hot2000 reports shows basement temps dropping to 14.5C in Jan, so I can infer that the average ground temp is <14.5C.
The weather data file I used has the deep ground temperature at -11.75C (and 3052 heating degree days for the average year too).
Paul in Montreal. -
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- CommentAuthorralphd
- CommentTimeFeb 9th 2009
Posted By: Paul in MontrealThe weather data file I used has the deep ground temperature at -11.75C (and 3052 heating degree days for the average year too).
Paul in Montreal.
Thanks. With the ground temp at 11.75C and high levels of insulation in the basement ceiling, 14.5C in Jan sounds reasonable for the first year of occupancy. It is not reasonable to use this as an estimate of long-term heat loss & temperature.
You could work around it by fudging the deep ground temperature, but figuring out what temperature to use is very difficult without geothermal modeling software. What I'd like to see is Hot2000 (or Hot3000 now since Hot2000 is approaching end-of-life) model the below-grade foundation heat loss for year 5 instead of year 1.
-Ralph
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