I have 3/4" oak over my radiant floors and designed the same for my brother, and many others, using panel radiators for the upper levels. I like a minisplit for the upper floors if the floor plan is open enough. We use many high velocity AC systems as well. You have to gauge the envelope and mechanical acquisition cost against fuel consumption, reliability, maintenance and naturally personal comfort. I am not a fan of electric "Cove" heaters. If you start with a hydronic system you can easily change your mind or have alternate fuel sources designed to the same distribution standard e.g. electric and wood boilers or heat pump with wood for winter.

I am very interested in the Daikin Altherma air-to-water heat pump for both low-temp heating and domestic hot water.

I am operating an Altherma in the Pacific Northwest where the climate is similar to yours. It has performed very well, but the control system for radiant heating represents an extra cost over the ductless minisplits that some have recommended. I would also worry about downsizing to the very small 18K unit, particularly if you hit a cold snap. When I bought, only the 30K and 54K units were available. If having a wood fired stove is part of your lifestyle, then having one could help make up the difference during cold snaps, however. Since your electricity costs tend to be a little higher, you want to stay away from using the back up heating options.

I would be surprised if the solar hot water option from Daikin would do anything for you there in Halifax. When I priced it the cost was about $4500 not including installation.

I went through the plans in detail and re-calculated my heat losses as follows based on requiring a 74F rise in temperature (-4F to 70F) and assuming 0.5 ACPH for the infiltration:

Area	sqft	R	BTU/hr
Walls	1,637	24	5,033
Ceiling	888	50	1,311
Floor	888	10	1,314
Windows	241	3	5,938
Doors	63	5	1,343
Skylight	16	3	500
Volume (cu.ft.)	13,248	0.018	8,799
TOTAL House			24,238
Garage			5,421
TOTAL			29,659

I guess I neglected to include the garage in prior calcs. For the garage, I assumed only 54F degree rise requirement (-4F to 50F) and R10 doors in the above.
The above is close to code-min envelope (code here requires only R40 for the ceiling). Then I repeated the calculation with an upgraded envelope and better windows and doors, plus R16 for garage door:

Area	sqft	R	BTU/hr
Walls	1,637	28	4,314
Ceiling	888	60	1,092
Floor	888	20	657
Windows	241	4	4,453
Doors	63	5	1,059
Skylight	16	3	375
Volume (cu.ft.)	13,248	0.018	8,799
TOTAL House			20,750
Garage			4,986
TOTAL			25,736

So, for my investment in a better insulated envelope, I reduce the heat loss by up to 4000 BTU/hr on the design temperature days. I don't know what COP would Altherma return at -4F, so I'll assume worst case scenario and pretend it switches fully to the 3kW backup, so COP of 1.0. At that COP rate and given 4000 BTU/hr=1.17 kW, I'm "spending" an additional 16.7 cents every hour if I have the code-min envelope. If I assume a crazy worst case scenario that every winter there's a 90-day period when I need the additional 4000 BTUs for 20 hours/day (extreme, I know!), that's 90*20*$0.167 = ~$300 every winter. So, assuming electricity rates stay the same (which they won't), every 10 years, I'll be paying at least additional $3000 in heating costs for having a weaker building envelope. The question is, how much will the upgrades cost to come up with a PV ROI.
Is that a correct comparison of the difference in the building envelope? Or am I just exposing the flaws of attempting to do energy modeling over a time-period using a design-day temperature approach?

Thanks again!

Posted By ICFHybrid on 28 Apr 2014 11:14 PM

I am very interested in the Daikin Altherma air-to-water heat pump for both low-temp heating and domestic hot water.

I am operating an Altherma in the Pacific Northwest where the climate is similar to yours. It has performed very well, but the control system for radiant heating represents an extra cost over the ductless minisplits that some have recommended. I would also worry about downsizing to the very small 18K unit, particularly if you hit a cold snap. When I bought, only the 30K and 54K units were available. If having a wood fired stove is part of your lifestyle, then having one could help make up the difference during cold snaps, however. Since your electricity costs tend to be a little higher, you want to stay away from using the back up heating options.

I would be surprised if the solar hot water option from Daikin would do anything for you there in Halifax. When I priced it the cost was about $4500 not including installation.

Thank you. I think given my re-calculation of heat loss above, I'd need the 30K unit. I'm not sure how a wood stove/fireplace would fit into our lifestyle, but I'm sure it would get a bit of use if we do get it. I'd like to have it for outage backup anyway, although a generator may be an answer to that as well.
The solar DHW system with a single panel here goes for about $4.5k+tax with $1250 rebate, so ~$4k net for the whole system. Source: http://www.thermo-dynamics.com/solar_boiler.html
I was hoping it would be cheaper with the Altherma since it already has the storage tank, but that would only save $500 and I'm not sure how much rebate I'd qualify for using this approach. But yes, the solar connection kit for the Altherma is quite expensive.
I thought solar hot water was a better bang-for-the-buck than solar PV these days, but given the numbers above, I wonder if it's better to have solar PV powering the Altherma instead to provide the DHW in the summer. I'll need to run the numbers to see how much power the Altherma needs for DHW and see if my tiny roof with 500W solar can supply enough power to keep the heat pump off the grid.

Since the ductless minisplits are being strongly recommended here, I'd like to understand how much would it cost me to be stubborn and go with radiant over a ductless system for the house. Based on this floorplan, how many ductless units would I need for the space and where would I put them?




Alternatively, I'd welcome input on the radiant design for this floorplan as well.

Posted By ICFHybrid on 28 Apr 2014 11:14 PM

I am very interested in the Daikin Altherma air-to-water heat pump for both low-temp heating and domestic hot water.

I am operating an Altherma in the Pacific Northwest where the climate is similar to yours. It has performed very well, but the control system for radiant heating represents an extra cost over the ductless minisplits that some have recommended. I would also worry about downsizing to the very small 18K unit, particularly if you hit a cold snap. When I bought, only the 30K and 54K units were available. If having a wood fired stove is part of your lifestyle, then having one could help make up the difference during cold snaps, however. Since your electricity costs tend to be a little higher, you want to stay away from using the back up heating options.

I would be surprised if the solar hot water option from Daikin would do anything for you there in Halifax. When I priced it the cost was about $4500 not including installation.

Perhaps putting too fine a point on it...

There is no location in the PNW except (at significant elevation) that has comparable winters to Halifax NS, and west of the Cascades mid-winter is more like April in Halifax.  The mid-winter binned hourly mean temp for the four coldest weeks of winter in Halifax is about 26F, which is the 99% outside design temperature for Seattle, whereas the 99% design temp for Halifax it +2F, with excursions well into negative digits F most years.

The mean mid-winter temps in Seattle are about 40F, which is about the mean temp in Halifax for the month of April.

The capacity of the Altherma at -4F (a pretty cold day in Halifax)  is dramatically lower than it's capacity at -4C (a pretty cold day anywhere west of the Cascades, and a heating design condition day in Seattle.)

First questions is why heat the garage? No real reason unless it is a shop space that you use daily. Put in a space heater for occasional use. Second, you are probably using incorrect inputs into the program. The walls- if they are R 19 in the stud bay + r5 continuous should be modeled as ~ 25%= R10.5 and 75% R24 this nets ~ R 18.2 Switching to 3 inches of outsulation bumps this up to 26 which is a significant Jump(40%). You are accounting for 8800 Btu’s from infiltration. That is a big number , that is 110 cfm of infiltration. I would think you are too high by a factor of 2-3 if you build the house correctly (well airsealed) + HRV for ventilation. As far as windows go, I would be looking at U 0.19 to U 0.16 triple pane windows so the r value of the windows would increase to ~ 5.3- 6.25 Why are you using -4°F as your design temp? Halifax seems to be tempered by proximity to the ocean. I would guess your 99% design temp is higher than that. Ashre calls the 99% number as 2°F so I would use 68° not 74 for my calcs The other thing that I think you need to rethink is the heatloss through the slab. IF you are slab on grade the heatloss from in floor radiant is much higher than if you use some sort of air heating system. Think about it this way- you are having the highest temperature surface in your house in contact with the ground- you will want R 16+ under the slab if you are going with a radiant. Depending on how you insulate the slab, I think your model is underestimating the slab losses with radiant. Before you go any further, recalculate the heat loss with the mods I gave you and see what you get Once you do that you have a better basis for decision making. Once you have a couple of options for heat loss, to get a crude number for yearly heating required Take the design heat loss / 68° delta = BTUs per degree per hour to heat the house Take that number and multiply it by the Heating degree days (base 65) * 24 Lets say the design heat loss was 25,000 btu’s, that equals 25000/68= 368 Btu’s per °F per hour Now if Halifax NS has 7860 HDD ( using °F) Your annual heat usage would be 368*24*7860 or ~ 69.5 Million BTU’s From that number you can figure out what your cost to generate those BTU’s are. Recalculate this based on a new heat loss calc and you have a way to compare rough performance numbers. Cheers, Eric

Posted By Eric Anderson on 29 Apr 2014 01:07 PM
First questions is why heat the garage? No real reason unless it is a shop space that you use daily. Put in a space heater for occasional use. Second, you are probably using incorrect inputs into the program. The walls- if they are R 19 in the stud bay + r5 continuous should be modeled as ~ 25%= R10.5 and 75% R24 this nets ~ R 18.2 Switching to 3 inches of outsulation bumps this up to 26 which is a significant Jump(40%). You are accounting for 8800 Btu’s from infiltration. That is a big number , that is 110 cfm of infiltration. I would think you are too high by a factor of 2-3 if you build the house correctly (well airsealed) + HRV for ventilation. As far as windows go, I would be looking at U 0.19 to U 0.16 triple pane windows so the r value of the windows would increase to ~ 5.3- 6.25 Why are you using -4°F as your design temp? Halifax seems to be tempered by proximity to the ocean. I would guess your 99% design temp is higher than that. Ashre calls the 99% number as 2°F so I would use 68° not 74 for my calcs The other thing that I think you need to rethink is the heatloss through the slab. IF you are slab on grade the heatloss from in floor radiant is much higher than if you use some sort of air heating system. Think about it this way- you are having the highest temperature surface in your house in contact with the ground- you will want R 16+ under the slab if you are going with a radiant. Depending on how you insulate the slab, I think your model is underestimating the slab losses with radiant. Before you go any further, recalculate the heat loss with the mods I gave you and see what you get Once you do that you have a better basis for decision making. Once you have a couple of options for heat loss, to get a crude number for yearly heating required Take the design heat loss / 68° delta = BTUs per degree per hour to heat the house Take that number and multiply it by the Heating degree days (base 65) * 24 Lets say the design heat loss was 25,000 btu’s, that equals 25000/68= 368 Btu’s per °F per hour Now if Halifax NS has 7860 HDD ( using °F) Your annual heat usage would be 368*24*7860 or ~ 69.5 Million BTU’s From that number you can figure out what your cost to generate those BTU’s are. Recalculate this based on a new heat loss calc and you have a way to compare rough performance numbers. Cheers, Eric

Thank you Eric! Much appreciated input!
I'm thinking that I'd use the garage as a shop space - not daily though, so a space heater might be more sensible as I was surprised by the significant heat load it would take to keep it at 50F. I'll have to price the additional zone and loop and see if that's worthwhile to me.

I still don't know the final true R-value of the wall. R24 is min code here and one builder is offering R28, so I'm trying to see what that additional cost gets me in heat load savings. So, should I be essentially treating the R24 as a true R19 for the heat loss calc? Or get a guarantee from a builder that they are using true final values in their quotes! :)

The infiltration calculation was just done from random info online. Most sources show 0.25-0.5 ACPH for tight new construction, so I wanted to be conservative. I'll bump that to 0.4 and see what happens.

Regarding the slab, after reading more it, I now understand your points. I found this explanation, so I will add slab perimeter losses @ R2 to the floor section losses. For the floor section slab losses, I assumed the ground temperature to be 55F, so my delta to indoor is 15F. Should I use a different value for that section? I cannot find any reference specific to Halifax, NS.

Thanks again.

Perhaps putting too fine a point on it...

As always, thanks for the correction, Dana, but we are North of Seattle and exposed to the Frasier River canyon blasts. We had 6000 HDD last year which is substantially more than Seattle, a heat island. I agree that it isn't the same as Halifax, but it is similar in that we do have extended periods of colder weather in which to see how equipment performs. And yes, we don't get quite the lows that Halifax gets, which is also why I pointed out he shouldn't short the Daikin. The proper sized Altherma with backup resistance heat could probably get him there in Halifax, particularly if they went for the auxiliary heat of a fireplace.

Personally, I think the lower initial cost of ductless minis is very attractive and since he seems inclined to some alternative tech, it would afford additional capital for that.

I am also finding that given a good envelope, fancy control strategies such as you can get with radiant, may be even more unnecessary.

We have software that simplifies the calculation of the annual/monthly heating BTUs required and the quantity of various fuels required to generate this heat in the manner that Eric suggested.

http://www.borstengineeringconstruction.com/Integrated_Heating_System_Performance_Calculator.html

You can enter zero for the climatic solar heat gain if you don't have any or don't want to include this.

Posted By sailawayrb on 30 Apr 2014 12:16 AM
We have software that simplifies the calculation of the annual/monthly heating BTUs required and the quantity of various fuels required to generate this heat in the manner that Eric suggested.

http://www.borstengineeringconstruction.com/Integrated_Heating_System_Performance_Calculator.html

You can enter zero for the climatic solar heat gain if you don't have any or don't want to include this.

That's a very helpful calculator! Thank you. Also, I used your heat loss calculator as well and came up with 21,428 BTU/hr.
I hope you don't mind if I post a screenshot of your calculator (Let me know if I should remove it.):



When I added slab perimeter losses to my calculation, it resulted in 22,956 BTU/hr, so I'm not sure where I'm off so much. I use the simple formula for all the areas (plus adding the slab perimeter loss): BTU/hr = Area * (1/R) * Temp Diff in F. Is that wrong? That loss is still with R24/R50/R10 structure with R3/R5 windows/doors, assuming 68F delta to air and 15F delta for ground/indoor diff and 0.5 ACH.
So, I'm puzzled by being off on my calculation, but will use your calculator instead.

Last year, Halifax had 3870 Celsius HDD, so that should be ~6800 Fahrenheit HDD, so I came up with my annual BTU demand at 51.5 MBTU or 15,076 kWH using the code-min envelope. Bumping the build up to R28/R50/R20 with R4/R5 windows/doors and lowering the ACH to 0.4, I get the design day heat loss down to 16,881 and the annual demand down to 40.5 MBTUs or 11,869 kWH. So, at $0.1425 per kWH, that's annual savings of $457 if I use electricity as a heat source.
All of this is without any climatic solar heat gain. Is this the correct approach?

How would I compare annual energy costs when using a heat pump? Is it as simple as (annual kWH / heat pump COP) * $/kWH? If I assume a seasonal COP of 2.5: (15,076 kWH / 2.5) * $0.1425 = $859  vs (11,869/2.5)*$0.1425 = $677

I'm not sure how much extra will it cost to go with the better insulated envelope, but at current rates (of course, the rates will only go up) and the annual savings of $182, the payback sure sounds a long way in the future.

Am I missing anything?

"I'm thinking that I'd use the garage as a shop space - not daily though, so a space heater might be more sensible as I was surprised by the significant heat load it would take to keep it at 50F. I'll have to price the additional zone and loop and see if that's worthwhile to me."---

IF you are using hydronic with freeze protection than you can use a fancoil heater in the garage on its own zone if you want fast and intermittent heat. (This may not work that well with a low tem emitter so check the water temps on the Dankin Unit)

If the wall is R19 in the stud bay + R5 continuous, it should be modeled as R 18 true for heat loss,

I would specify, in writing that I expect blower door testing and an ACH50 of 2. This then works out to about~ 0.1 ACHN Since infiltration starts to be a huge chunk of the heat loss when you get to higher insulation levels, it is important to get it dealt with properly. You will need to add back an air exchange method- an HRV is ideal and minimizes heat loss. If you use ACH50 of 2 and a moderate efficiency HRV to get you to comply with ASHRE62.2- 2010 ventilation requirements, you can use 0.175 ACHN for your infiltration number and be safe.
ACH50 is air exchanges at 50 Pascals of depressurization, ACHN is air exchanges under normal conditions of stack effect and wind.

“Regarding the slab, after reading more it, I now understand your points. I found this explanation, so I will add slab perimeter losses @ R2 to the floor section losses. For the floor section slab losses, I assumed the ground temperature to be 55F, so my delta to indoor is 15F. Should I use a different value for that section? I cannot find any reference specific to Halifax, NS. “----
This is kind of vague as far as modeling goes, Once you get down ~ 6 ft the soil temps are stable at around the yearly average temp which looks like it is ~50° for Halifax. If you are slab on grade, the perimeter heat loss dominates the equation. I would use 50° F for the center slab temp. You should be looking for a slab that is completely thermally broken from the footing if possible.

Cheers,
eric

Last year was an exceptionally mild winter for Halifax temperature-wise. The extreme warmth that hit in mid-March followed by above-average temps that hewed considerably below typical HDDs.   The 30 year average for Halfax is 4367 HDD ( 7860 HDD-F ).  During an exceptionally cold year you could hit 5000 HDD-C.  For energy use estimation purposes it's probably better and more accurate to use 4300 HDD, not 3870HDD, unless you have a climate model (crystal ball?) telling you the local climate is warming more rapidly than the world average.

The ~4400 / ~7900 HDD average is why it's  really a zone 6 climate, despite the 99% outside design temp & typical coldest-day temperatures more typical of zone 5 locations:




When comparing energy costs against building envelope, bear in mind that the heat pump has to be replaced on a 20-25 year schedule, whereas the building insulation should be good for 50+ years, high-performance windows 25+ years.  If you run a lifecycle present-value calculation using reasonable discount rates and include ANY reasonable energy price inflation, designing the building upgrades to break even in 50 years at 1.5-2% annual energy price inflation is a pretty good hedge against future energy prices in the event of a spike.  (But if the Sanford Bernstein analysts turn out to be correct ,energy inflation will halt or even reverse and become deflationary before Y2030.  I wouldn't bank on that just yet, but there is at least some real analysis behind their argument.)

When looking at the equipment efficiency relative to the energy price it needs to be evaluated on something like a 20-25year lifecycle basis, at which point major components will need to be replaced. (If hydronic, the radiation is probably good for 50 years, but the pumps & boilers/heat-pumps etc are 20-25 year items.)

With a Mitsubishi "FH" single head mini-split solution your annual average COP will be over 3.2, with the Altherma it all depends on your radiation relative to the heat load.  If the water temp requirements never exceed 35C it should deliver about 3.0, but if it needs to be 45-50C to deliver the heat at your 99% design condition it'll probably average no better than 2.0- even less if you undersize it and causing over-use of resistance heating.

Thank you Dana. I used this source for my HDD data: http://halifax.weatherstats.ca/charts/hdd-25years.html
The last 25 years shows:
Max - 4400 / 7920
Min - 3400 / 6124
Avg - 3915 / 7048
So, it does sound like Halifax is heating up! :) I'll bump up my HDD to 7048.

Yes, I have to amortize the costs of the equipment over its lifespan. A 25-year cycle would work well with mortgage amortization too.

The 3.2 COP does sound very attractive. How many of the Mitsubishi FH minisplits would you recommend for my floorplan above?
I guess with using minisplits, I'd need to add a cost of a separate DHW heater as well.

Posted By eljay on 28 Apr 2014 08:02 PM
Regarding solar, I have attached the proposed hip roof line as opposed to a gable roof and showing the orientation of the house.


The yellow areas I think are the only ones were I can think about solar panels in the future. On the front (left) is a garage attached on the main level, so I'm sure half the roof will be in shade for significant portion of AM sun. The yellow area on the larger roof is 144 sqft in total (SSW orientation), so I figure it will hold two 5x3' 250W panels. The thermal panels from a local supplier are 4x8', so I could likely only fit one on the garage roof for DHW. That's not much of a solar potential. :(

It is a small lot (50x100), so I don't have much freedom on house orientation and the back yard is already small.
Given those constraints, is it worth making the house "solar ready" now (wiring, roof terminals etc.)? I'd like to say 'yes' because I'd love to have it but don't see much potential in that drawing beyond DHW solar unless you fine folks can suggest a design change that will work (btw, having a gable roof running left to right would look very odd in this neighbourhood).

According to your drawing, you have house roof surfaces that point SW and SE, with the larger surface pointing SE. I assume that your "N" arrow might not be accurate in the drawing, but if it is, than using the SE side of the roof, which is a larger area than the SW side, would be an option for solar collectors. In my location, because of clearer weather and lower temperatures in the morning, I would get more energy pointing SE than SW. (Luckily, I have roof areas (after redesign) that point SSE, and those work well for solar.) If you really do have a SE orientation for part of your house roof, then you could make that portion of your roof and gable roof, and have a lot more area to work with.

I had mentioned changing the design of the roof on both my house and my garage independently. I should have mentioned that I have a detached garage, so it is easier to change the design of the two separate roofs! Not so easy with an attached garage.

Dont forget solar south is 22° West of Magnetic south in Halifax. YOu could always get creative and go for a 4:12 pitch shed roof on the long axis. Or move the garage to the shoth and go for more of a L shape. don't know how this would work with the layout though.

cheers
Eric

Eljay, glad that you found our calculators to be helpful and there’s no need to remove the screenshot. You selected option 3) slab-on-grade floor which uses the following equations to determine the floor heat loss:

if (eftype==3){
'Insulated Slab-on-Grade Floor (Calculation based on Perimeter and Siegenthaler F-Value)'
fvalue=1/(1.21+0.214*efr+0.0103*Math.pow(efr,2));
efhlbtuph=fvalue*efaop*deltatdegf;
}

efr is the slab insulation R-value. The slab is assumed to be insulated both below the slab and at the perimeter.

efaop is the perimeter.

deltatdegf is the difference between the design indoor and outdoor temps.

Posted By sailawayrb on 02 May 2014 12:32 PM
Eljay, glad that you found our calculators to be helpful and there’s no need to remove the screenshot. You selected option 3) slab-on-grade floor which uses the following equations to determine the floor heat loss:

if (eftype==3){
'Insulated Slab-on-Grade Floor (Calculation based on Perimeter and Siegenthaler F-Value)'
fvalue=1/(1.21+0.214*efr+0.0103*Math.pow(efr,2));
efhlbtuph=fvalue*efaop*deltatdegf;
}

efr is the slab insulation R-value. The slab is assumed to be insulated both below the slab and at the perimeter.

efaop is the perimeter.

deltatdegf is the difference between the design indoor and outdoor temps.

Thank you! Since the formula is using the air temp delta, wouod it be overestimating the heat loss at the design temp since the ground temp in the centre of the slab is typically a little higher?

Posted By Lee Dodge on 30 Apr 2014 03:45 PM

According to your drawing, you have house roof surfaces that point SW and SE, with the larger surface pointing SE. I assume that your "N" arrow might not be accurate in the drawing, but if it is, than using the SE side of the roof, which is a larger area than the SW side, would be an option for solar collectors. In my location, because of clearer weather and lower temperatures in the morning, I would get more energy pointing SE than SW. (Luckily, I have roof areas (after redesign) that point SSE, and those work well for solar.) If you really do have a SE orientation for part of your house roof, then you could make that portion of your roof and gable roof, and have a lot more area to work with.

I had mentioned changing the design of the roof on both my house and my garage independently. I should have mentioned that I have a detached garage, so it is easier to change the design of the two separate roofs! Not so easy with an attached garage.

That's encouraging to hear that even without a perfect orientation, solar could work well.

Here's a better reference drawing:


I have oriented the houseplan according to true North/South and also overlaid the sunshine radius (from suncalc.net) that the housesite would get on July 1s. The line in the middle shows noon sun position.

I have also added a red line across the main roof to show how the gable roof would look instead of the hip roof.

Essentially, with a gable roof, the large plane would be facing fully SE. With the hip design, I'd be getting a small portion of the roof facing ~210 degrees (somewhere between SSW and SW).

I'll have to find out how much solar efficiency I'd get from a panel on the SSW side with a hip roof versus keeping that same collector on the SE side of the roof. If the gain is negligible, then I'd rather stick with the cheaper gable roof and spend the savings on an extra panel or two on the SE side.

“Thank you! Since the formula is using the air temp delta, would it be overestimating the heat loss at the design temp since the ground temp in the centre of the slab is typically a little higher?”

Well Eljay, not according to Siegenthaler (a professional engineer recognized to be the authority on hydronic radiant concrete slab-on-grade floor heating) and others who have extensively studied slab-on-grade floor heat loss. The vast majority of slab-on-grade floor heat loss occurs at the exposed floor perimeter (which is exposed to the outdoor temp) and not in the center section of the slab (which is exposed to the ground temp). So outdoor temp and exposed floor perimeter is used for estimating slab-on-grade floor heat loss. However, if you have a basement floor that is entirely below the frost line, it would indeed be appropriate to use the ground temp and the floor area for estimating this basement floor heat loss.