NORTHEAST (New York) installing new walkway 225 sq ft (15×15) am interested in installing under pavers electric heating coil; to prevent icing in winter for mother-in-law
1) best system
2) how should wire be laid out?
3) will this increase tendency to crack or heave in winter or ruin brick?
Replies
Hmmmm...
I'm not convinced that you'll get the heating you need out of an electric system. One rule of thumb I've seen is between 100-150 BTU/sq ft, so even a small area turns into a big load in a hurry. Can the electric system handle the load, and for that matter, can the MIL handle the electrical bill this will entail?
If she has a boiler, a separate zone with a HX is probably a better way to go.
100 BTU/hour works out to 29 watts/square foot, which is about 6.5KW for the space, or around 27 amps at 240V. Not a small load, but manageable for most modern electrical systems. However, it would probably be best to have it broken into 2-4 sections to manage the load -- only deice one section at a time.Pavers are probably a better choice than solid concrete, from a cracking point of view. However, with pavers you can't imbed the heating coils in the paver itself, reducing the rate of heat transfer, and the thickness of the paver will also reduce the effectiveness of the system. Plus, if you have dry-set pavers you can't put foam insulation under them very readily as it won't bear driveway loads.
If ignorance is bliss why aren't more people
happy?
Hi Dan,
Thanks for your thoughts. I agree that the load for such a small area can be managed on an electrical system, but some thought will have to go into how to activate and control the system or the MIL will make the local utility much too happy.BTW, I didn't want to advocate concrete as the top layer, though it can be done. I've heard of contractors using PEX-in-concrete as an underlayment for pavers or even asphalt, depending on what you're trying to heat. I've even heard of PEX tubing being covered (carefully!) in asphalt. Some foams have very impressive compressive strengths. Depending on how the concrete slab is constructed, they can even deal with the weight of fully-loaded garbage trucks passing overhead (so many tons on 12 sq inch of tire tread)... Part of the trick is to ensure that the compaction below is done properly. According to hot rod, many installations, when tested, fail in this regard.
Yeah, ideal for controlling the heaters would be to have imbedded thermostats (probably drilled into pavers so they'd be close to the surface) and a sequencer that would run a segment until a target temp was achieved for a specified period of time, then go on to the next segment. But that's probably a $5-10K control system.Simpler would be a unit that would run each segment, in turn, for a fixed period of time. Could probably build that for around $500 if you were lucky. For a bit less you could rig contactors and a rotary switch, to only power one segment at a time with manual switching.
If ignorance is bliss why aren't more people
happy?
Holy Smokes! I built a system similar to what you describe and embedded it in the slab for my shop to monitor radiant heating. Eight zones with six sensors in each zone. Each zone samples the sensors and squirts the data over a serial line to a central controller for heater, pumps, etc.
I figure I spent $175, tops, on the parts (not counting the investment in my programming language compiler). For $10k, I'd ought to get into the business!
Yeah, I was including the cost of the computer, programming, and contactors, plus casing it all up.
If ignorance is bliss why aren't more people
happy?
I cased mine in a short chunk of PVC pipe and sealed the wires coming out with epoxy...
In Ottawa our weather has changed in the last 15 years or so, it's not the snow that gets us as much as the perpetual freezing rain. You finally get it hacked off the laneway and wham, you get more .. I've found 3 neighbours laying in laneways in the last 4 or 5 years, broken hips, broken ankles, shattered confidence .. ice melt systems make sense, it only takes a bit to clear the ice, versus a bad break!
There are probably times when the potential for human injury justifies the energy cost. And yes, it's a good use for waste heat. However, it galls me just a bit when I see blatant overuse of energy to save some lazy rich guy the trouble of sanding the driveway....Andy Engel
Senior editor, Fine Woodworking magazine
Never try to teach a pig to sing. It wastes your time and annoys the pig.
Other people can talk about how to expand the destiny of mankind. I just want to talk about how to fix a motorcycle. I think that what I have to say has more lasting value. --Robert M. Pirsig
None of this matters in geological time.
Go to the Tyco Thermal webpage at http://www.tycothermal.com/usa/english/snow_melting/applications/industrial/walkways_ramps_and_steps/electromelt_system/default.aspx This stuff uses self-regulating cable so it automatically adjusts the output as required for temperature. If you click on 'Literature' at the top of the page you can go to a design guide, which will help you figure out what you need.
My buddy's doing one now about 40 x 40. They went with pex in concrete, over compacted base and insulation. Then it will be covered with pavers. he was actually given the job by the electician, so I suspect the pex is a better system.
Don K.
EJG Homes Renovations - New Construction - Rentals
You can download the SIM presentation we did for ISH/RPA...
http://www.healthyheating.com/downloads/Snowmelt.pdf
Pull from it what is useable and if you have any questions on the rest let me know.
RBean
web: http://www.healthyheating.com
blog: http://wonderfulwombs.typepad.com
I've got to wonder if a driveway melt system, even at Grandma's house, is environmentally defensible? I wouldn't think so. Andy Engel
Senior editor, Fine Woodworking magazine
Never try to teach a pig to sing. It wastes your time and annoys the pig.
Other people can talk about how to expand the destiny of mankind. I just want to talk about how to fix a motorcycle. I think that what I have to say has more lasting value. --Robert M. Pirsig
None of this matters in geological time.
Hi"I've got to wonder if a driveway melt system, even at Grandma's house, is environmentally defensible? I wouldn't think so."I'd 2nd that -- think about the tons of coal being burned to generate the electricity just to melt some snow -- can't you hire the kid next door to shovel it?Gary
I'm with you. Nothing drives me battier than snowmelting systems... the loads are just sooo huge. maybe for *must clear* areas like ambulance ramps, I could see it, but residentially, it's just a gigantic waste of energy.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
Agreed, for melting substantial amounts of snow it's a big waste. But for deicing, where 15-30 minutes of operation will often be enough, it's not so bad.
If ignorance is bliss why aren't more people
happy?
I agree that most residential snowmelt applications are not environmentally defensible. However, they have their place. For example, someone who is wheelchair-bound or reliant on crutches will surely benefit greatly from the lack of ice or snow on the ground. Similarly, the economics can also make a big difference. I know one HO that pays a professional landscaper in excess of $100 for every visit to clear her 70' walkway to the street, and a 70' driveway (using a plow for the latter, mind you). Even at $2 a therm, I could buy an awful lot of gas to heat that driveway.
Of course, you're missing the $10k initial charge for the system in the first place there constantin ;) random but ballpark number there.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
A lot cheaper than raising a kid. Will work harder too, and no complaints.
If ignorance is bliss why aren't more people
happy?
Hey, good point, I'll have to suggest that to my fiancee :D-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
"A lot cheaper than raising a kid. Will work harder too, and no complaints."
Yeah, but when you get home from a long day at work the driveway never says
"Yay, Daddy's home!!!"
Tom
Douglasville, GA
You're right, of course, but the actual cost depends entirely on the situation. A hydronic snowmelt system can perhaps cost less if it's installed when the rest of the house is getting poured/plumbed for hot water heat... but you would know this better than I.For me, the limitus test is in the actual application. A kid with a scraper may not be able to get all the stuff off the driveway/walkway. If covering an a walking approach from above is not an option, then a snowmelt system in a very limited area might make sense. Not the whole driveway, mind you, just the area where the person on crutches or the wheelchair needs to travel.I wouldn't put in a snowmelt out of principle in my own home but I respect the possibility that there are applications out there where they can be justified.
Even considering my conservative Republican leanings, there are issues other than money at play here. Money is just an abstraction of scarce resources.Andy Engel
Senior editor, Fine Woodworking magazine
Never try to teach a pig to sing. It wastes your time and annoys the pig.
Other people can talk about how to expand the destiny of mankind. I just want to talk about how to fix a motorcycle. I think that what I have to say has more lasting value. --Robert M. Pirsig
None of this matters in geological time.
Have a read at these excerpts and then in your collective minds eye scale up the environmental impact by the number of houses in <!----><!----><!---->America<!----><!---->.<!----><!---->
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“…single-family, detached houses account for 63% of total dwelling units in the <!----><!---->United States<!----><!---->.”<!----><!---->
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“Average household size in the <!----><!---->United States<!----><!----> has dropped steadily from 3.67 members in 1940 to 2.62 in 2002. The average size of new houses increased from about 1,100 ft2 (100 m2) in the 1940s and 1950s to 2,340 ft2 (217 m2) in 2002. Factoring together the family size and house size statistics, we find that in 1950 houses were built with about 290 square feet (27 m2) per family member, whereas in 2003 houses provided 893 square feet (83 m2) per family member (NAHB 2003)—a factor of 3 increase.” <!----><!---->
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“As house size increases, resource use in buildings goes up, more land is occupied, increased impermeable surface results, in more storm-water runoff, construction costs rise, and energy consumption increases.”
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Ref.: Journal of Industrial Ecology, Winter-Spring Edition Authors from Massachusetts Institute of Technology and <!----><!---->Yale<!----> <!---->University<!----><!---->.<!----><!---->
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The icing on the cake perhaps is this….“Builders Prevail Against Costly Energy Code Change…NAHB prevailed in an effort to roll back new, more stringent insulation requirements at International Code Council hearings in <!----><!---->Detroit<!----><!----> on <!---->Sept. 29, 2005<!---->”<!----><!---->
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Is it environmentally defensible when the number of people per home is going down at the same time as the size is going up all whilst the cost of fuel is rising and the lobbyist who never have to pay for the operational costs have scuttled an attempt to improve housing performance? We, the consumers of North America support this behavior everytime we build a new home to minimum standards. I’ll go out on a limb here and state that consumers as a whole don’t understand that building codes are "minimum"…it’s a “if its build to code it must be good mentality.” Most are completely unaware of the politics of the industry…one of the reasons for the rejection of the higher standards was the” cost of affordability”…Cost of Afforabilty? The data says you can build big or you can build efficient…environmentally the data is suggesting we’re making bad decisions to support a well oiled machine called the housing industry. The census data (if you believe it) also suggest that the number of electric and hydroninc radiant systems remains below 5% of all HVAC systems. I don't have specific data for residential snow melt systems but it falls within the radiant category.
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I’m in total agreement that snow melting - out of context - is definitely not environmentally defensible nor is building bigger and finer homes for fewer occupants ( a much bigger and more real issue - you can turn off a snowmelt - the options for big inefficient homes are few.) …each rain drop contributes to the flood…IF grandma’s snowmelt is attached to house that has a better energy consumption ratio per person/sq.ft then the dear little old lady is statistically going against the grain of the rest of the country - perhaps following grandmas’ footsteps would be a lunge in the right direction. RBean
Edited 11/15/2005 2:04 pm ET by RBean
Good analysis, except that you only scratched the surface by mentioning NAHB defeating the new energy code. That's more complicated than the headline makes it appear.Andy Engel
Senior editor, Fine Woodworking magazine
Never try to teach a pig to sing. It wastes your time and annoys the pig.
Other people can talk about how to expand the destiny of mankind. I just want to talk about how to fix a motorcycle. I think that what I have to say has more lasting value. --Robert M. Pirsig
None of this matters in geological time.
I support and practice energy conservation, however two points.
I am talking about 200 sq ft which would be used infrequently. In the scale of energy use it would be minimal.
A fractured hip would be far more enviromentally cruel to my mother in law.
Sorry if I came on a bit strong. I did mean to say that there are circumstances as with your mil that can justify such consumption. My gripe is more with those who thoughtlessly and indiscriminately throw resources around.Andy Engel
Never try to teach a pig to sing. It wastes your time and annoys the pig.
Other people can talk about how to expand the destiny of mankind. I just want to talk about how to fix a motorcycle. I think that what I have to say has more lasting value. --Robert M. Pirsig
None of this matters in geological time.
I couldn't agree more, Robert. We seem to continue to miss the signals that the market and the energy providers are sending us. Energy won't always be cheap and building homes as if it was will bite homeowners in their rear ends eventually.My very limited understanding of the NAHB controversy re: wall insulation is that they successfully resisted the DoE efforts to raise the wall insulation bar by two R-notches, going from R11 and R-19 to R13 and R21. The actions of NAHB are entirely understandable, considering they're being paid to keep building standards as cheap as possible. However, is it to the benefit of the homeowners to prevent better insulation standards coming into effect? Some people go as far as advocating a ban on fiberglass in exterior wall insulation applications... calling for dense-pack cellulose as a better, greener alternative that has a better in-field track record than fiberglass. Now there would be an interesting can of worms to open.
The NAHB headline as Andy says doesn't tell the whole story...it is bigger than that of course and I stopped following the procedures as soon as I saw the reasoning for the direction it was heading...can we apply / use the cliché - "marketing masquerading as science" here? Perhaps. Andy your comments and insight here would be valued.<!----><!----><!---->
Constantin has also asked a key question... is it to the benefit of the homeowners to prevent better insulation standards coming into effect? <!----><!---->
Here in Canada, the R 2000 program from a purely economic perspective should have been canned years ago...but its existence set a benchmark to which energy efficiency is measured.<!----><!---->
What is the long term environmental cost of minimum standards over a growing inventory of inefficient homes? <!----><!---->
What is the benefit and to whose account is it credited for not raising the minimum standards?<!----><!---->
Follow the money…and the honey pot and Poo bear will be near by.<!----><!---->
RBean
web: http://www.healthyheating.com
blog: http://wonderfulwombs.typepad.com
As I understand the story, the new code would have made it impossible to acheive the required R-values with anything other than foam or hi-density fiberglass. This provision was supported by the fg industry, opposed by the cellulose industry. More to the point in my mind is that it's questionable that fg batts ever acheive their stated R-values in residential construction. Cellulose and blown fg might not acheive the proposed code's r-values, but what they manage is far more reliable, particularly as the temperatures drop, than can be acheived with batts.
Until R-value has more value as a measurement than as a marketing tool, we'll continue to have similar debates. You could enlarge this question to cover the entire code writing process, parts of which seem to be every bit as much about promoting special interests as about promoting sound building practices. That opinion, btw, is mine and is not intended to represent my employer's views.
AndyAndy Engel
Senior editor, Fine Woodworking magazine
Never try to teach a pig to sing. It wastes your time and annoys the pig.
Other people can talk about how to expand the destiny of mankind. I just want to talk about how to fix a motorcycle. I think that what I have to say has more lasting value. --Robert M. Pirsig
None of this matters in geological time.
I suppose the question of achieving the desired performance also needs to factor in the thickness of exterior wall studs. Any R-value can be achieved, given enough wall thickness. It is my understanding that the NAHB opposed the change because it wouldn't allow builders to continue using 2x4's and cellulose/fiberglass in exterior framing. I am not familiar with all the issues that go into framing, but I was under the impression that exterior walls of 2x6 on 24" centers were largely comparable to 2x4 walls on 16" centers. Yet, the former gives you far more insulation potential than the latter.
Constantin...you're getting to the meat of the debate...it’s another form of mad cow syndrome...the equivalent to a girls gone wild video except it applies to the logic vs politics in housing. They needed you in <!----><!----><!---->Detroit<!----><!---->...quit playing with that fancy boiler of yours and get out of your basement - American's needed you and your collective then and now to pour a dose of reality onto the fire. (grin)<!----><!----><!---->
<!----><!---->
Here's more fuel from a survey conducted by ASID on Aging in Place…<!----><!---->
<!----><!----><!----> <!----><!---->
“Given a choice, the majority of people will remain in their current homes as they age – even into retirement. More than three-quarters are extremely likely (55%) or somewhat likely (22%) to stay.” This is similar to NAHB's own 2002 National Older Adult Housing Survey and the 1999 Round Table discussion on Changing Demographics.<!----><!---->
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Was the relationship between demographics, energy cost over fixed income and product offering (i.e. size) debated? <!----><!----><!----><!---->
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I agree the approach to change the benchmark was suspect but the message is right and the end results would have better served a significant portion of the population.<!----><!---->
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Do consumers want big vs efficient? (see the surveys...ask Sarah Susanka)<!----><!----><!----><!---->
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Were they represented at the meetings? (don't know)<!----><!---->
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Does it matter? (to millions approaching retirement on fixed incomes it does)<!----><!---->
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Wish I could have been in <!----><!----><!----><!----><!---->Detroit<!----><!----><!----><!----> for the fireworks!
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RBean<!----><!---->
web: http://www.healthyheating.com<!----><!---->
blog: http://wonderfulwombs.typepad.com<!----><!---->
Edited 11/17/2005 8:59 am ET by RBean
There's a debate. Structurally, I don't think there's an important difference, but there are many here who would see me publicly humiliated in the stocks for saying so. You're right about the thermal performance, for certain. Although 2x4s with cellulose or fg and sheathed with foam would probably outperform a conventionally sheathed 2 x 6 wall.Andy Engel
Senior editor, Fine Woodworking magazine
Never try to teach a pig to sing. It wastes your time and annoys the pig.
Other people can talk about how to expand the destiny of mankind. I just want to talk about how to fix a motorcycle. I think that what I have to say has more lasting value. --Robert M. Pirsig
None of this matters in geological time.
I think you missed the point.Installing a complicated driveway electric snow melting system - A pretty big expense.Using irreplaceable fuels to melt snow which could be easily and cost effectively shoveled - environmentally indefensible.The opportunity to run a driveway clearing system just enough to convert the snow into black ice so your MIL slides off the side of a mountain - priceless.
Roger that.Andy Engel
Senior editor, Fine Woodworking magazine
Never try to teach a pig to sing. It wastes your time and annoys the pig.
Other people can talk about how to expand the destiny of mankind. I just want to talk about how to fix a motorcycle. I think that what I have to say has more lasting value. --Robert M. Pirsig
None of this matters in geological time.
My northen neighbor, Wiconsin, has via their energy conservation code, forbidden the use of snowmelt systems that are not 100% waste heat powered.
Edited 11/16/2005 4:57 pm by Tim
Yeah, this is the kind of regulation we need. Heavy-handed, blind, and stupid.
Wastewater exchange is a great idea for a hotel, retaurant, or other high water user, though exchanging it back to preheat potable water might be more efficient, and would add value year round.
The thing about snowmelt is that much of the demand is driven by litigiousness. One lawsuit can pay for a lot of energy.
As for using snowmelt to make the disabled more self-sufficient, I think it can be 'defensible'.
A covered walkway is often a better option, but those are not always practical, or allowed by building regs.
I've often thought that the ultimate snowmelt system would be a groundwater exchange system. Just a matter of having enough exchange capacity, and moving enough volume to get the BTUs.
Go here http://www.bylinusa.com and see what they have.
I live in New York's Adirondack region, high peaks area, my elevation is 2,000 ft, and the best driveway heating system I know of is Florida sunshine!