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Hannah B's Inc
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Posts:4
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| 01/15/2009 12:38 PM |
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Has anyone had any experience with Radiant Heat Film?
We are planning on building a 10 unit apartment complex for affordable living. The building will be ICF construction with the roof joists foamed in. The heat loss calculations coming in around 9-10 btu/ ft, the apartment will be 1000 sq. ft on 2 floors. The most efficient system we seem to find is an electric heating set up. We found radiant film in rolls that would be perfect for the ICF application. Any thoughts?
Steve
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BadgerBoilerMN
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Posts:311
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| 01/15/2009 6:31 PM |
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| how do you define efficiency? |
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MA
www.badgerboilerservice.com |
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Hannah B's Inc
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| 01/16/2009 7:56 AM |
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Electric heat is 100% efficient. Due to the fact our units are only 960 sq. ft, it would be difficult to install other types of heat sources that would get the overall BTU's down to 9,000 or so. With electric heat you can size the BTU/ Watts to a very accurate amount. My question was " has anyone had any luck using the film".
I have used electric basebaord heating for years with good results - except for the exposure and possible damage in a low income application. |
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BadgerBoilerMN
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| 01/16/2009 9:22 AM |
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Efficiency and economy or easlily confused. The cost of heating with electricity vs. natural gas for instance can be twice to three times.
Whereas the energy transmission efficiency for electric resistance heating may come close to 100%, when calulating real efficiency one has to go back to the power plant. The conversion from coal, to steam, to turbine, to usable electric power, is a very inefficient process. We must then add the transmission losses.
In the end we use about 30% of the energy we actually create. That is not 100% efficient.
As to the size of your application, a Combi1 with hydronic radiant floors would be the perfect match.
You did mention "affordable" living.
As for "film" I suspect you refer to low voltage matts. The folks at Zmesh will tell you what you want to hear.
As 57% of our electricity is generated by coal-fired power plants, the idea that electric resistance heat is Green or efficient, is junk science. |
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MA
www.badgerboilerservice.com |
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Hannah B's Inc
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Posts:4
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| 01/16/2009 10:26 AM |
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| Thanks for your help. This apartment complex will be in a low income area. What exactly is a combi1 with hydronic radiant system? |
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BadgerBoilerMN
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| 01/16/2009 10:41 AM |
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http://www.bradfordwhite.com/images/shared/pdfs/specsheets/542b.pdf
I use them regularly in my design work and local installations. The Combi combines space heating AND domestic hot water (the second largest household fuel bill) safely and efficiently. One appliance takes up the physical footprint and does the work of two. Labor is cut down and the operating cost (more important for the poor) will usually be considerably less depending on local fuel prices.
An 82% water heater is then Greener than "100%" electric resistance since natural gas has half the carbon footprint of coal.
This is not to be confused with the silly "open" heating systems, so often mentioned on the net.
You are welcome.
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MA
www.badgerboilerservice.com |
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Dana1
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Posts:702
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| 01/16/2009 3:06 PM |
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Be very careful about reading between the fine-print lines when reading specs for "radiant films", since they're heavily hyped. Where & how you use them and near-perfect installation make a huge difference in actual performance. When it doubt, spend the money on high-performance plastic insuation (which is sounds as if you've already done.) Where cost is an issue, in most non-ground-contact situations cellulose is an excellent plan-B. NEVER count on radiant barriers as a primary insulation layer (unless you're in a vacuum enviroment that requires an astronaut suit. :-) ) Convection & conduction issues can defeat radiant barriers pretty easily.
What BadgerBoilerMN said about efficiency of electric vs. natural gas. Until the grid is a heluva lot greener than it is today, it's the worst from an environmental point of view (and in most places significantly more expensive.) In milder climates air-coupled heat pumps can be cost & efficiency competitive with NG though. Ground or water- coupled heat pumps (aka "geothermal") are almost always efficiency-competitive with NG, but generally cost quite a bit more.
In 10 unit buildings or larger it's often more efficient, space efficient, and construction cost-competitive to run a single hot water heating system as a heat exchanger (eg. Ergomax E44) running off a mid or high-efficiency gas fired boiler, rather than 10 separate tanks/tankless units. Whether that's the right thing to do for THIS building depends somewhat on the layout- you don't want to have any apartment calling hot water more than 40-50' from the heat-exchanger or the distribution losses and water waste (as well as user-satisfaction for the unit on the end) suffers. There may be other issues too, particularly if water is metered separately per apartment. Depends on the architecture- might be possible.
With the low per-unit heat load, from a construction cost and overall efficiency point of view it may be the "right" thing to include heat in the rent, and have 1-2 boilers feeding a central buffer tank and 10 zone pumps (one for each apartment). In well insulated buildings it's not tough to design for (and relatively cheap to install) hydronic baseboards to run a lower water temps. The old standards were to design for 160-180F water, but it's significantly more efficient to add enough baseboard to deliver the design-day heat at 140F, and control the temperature of the tank with an "out door reset" type control that backs off the temp to 110F or so on very mild days/nights, but ramps up the temp when it's colder out. Full-on radiant slab floors/ceilings can run even more efficiently at even lower temps, but if the floors are wood they'll likely need 140F water on design-day heat loads anyway. Find a good heating contractor to figure/spell it all out for you, but low temp baseboards, while not as cushy as radiant, are still pretty comfortable, with somewhat faster response times than radiant (and can more appropriately use nighttime setback thermostats, etc.) |
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Hannah B's Inc
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Posts:4
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| 01/16/2009 3:56 PM |
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Thanks Dana,
Lots of good ideas. Are you saying that radiant films shouldn't be used? With accurate film installation you can adjust the load perfectly and evenly and the upfront cost is relatively low. Seems like the way to go and each tenant would pay for heat through their electric bill. |
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Dana1
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Posts:702
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| 01/16/2009 4:37 PM |
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Perhaps I'm misunderstanding what you mean by "radiant heat film" (which I took to mean a reflective film, often referred to in the trades as "radiant barrier".) Got a product name I can google up?
Any electric-powered radiant heat will be 2-3x more expensive to operate than an air-source heat pump (most of which are set up to run as air-conditioners as well) but may be somewhat more comfortable. It'll be more space-efficient, as well. But all resistance-electric heat is the ANTITHESIS of efficency from a utilization of fuel point of view. In electric power generation 60% of the consumed energy goes up the flues and cooling towers without ever leaving the powerplant. Another 7-10% of the energy is consumed by the transmission grid, leaving you with a 65-70% loss by the time it gets to the meter hookup on the building. For space heating, only heat-pumps can make up for any of this loss by utilizing low-grade solar heat stored in the air/ground/water.
By comparison, about any appropriately-sized mid-efficiency gas heating system will deliver at least 75% of the fuel-energy as space or water heat, wasting only 25% up the flues. For more money, modulating & condensing boilers will deliver at least 85%, sometimes more than 90%. Sizing a boiler for individual units with a design-day heat load of 9kbtu/hour is nearly impossible (they just don't make 'em that small!) Small side vented wall furnaces in the 10-15kbtu/hour exist, and will deliver 65-70% of the energy as heat to the inside.
But small gas-fired combined HW & heating systems can easily be designed to cover both heat & hot water with higher overall efficiency than any pairing of separate heating & hot water systems. BadgerBoilerMN is putting you on the right track. This is a case where the heating load is a fraction of even a smaller standard tank HW heater's burner output. Using it to heat the space as well as hot water improves it's efficiency by increasing it's duty cycle (which reduces it's standby losses.) If natural gas is available, it's by far the better-greener-cheaper approach. If the heating systems MUST be electric- heat pumps are the way to go. (They can be pretty small too- 1 ton heat pumps are tiny, cheap and up to the task, if your heat load estimates are accurate.)
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dmaceld
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Posts:805
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| 01/18/2009 12:41 AM |
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Hannah, please don't be off put by the responses you've gotten so far. As a primary heating source electric resistance heating is as welcome in this forum as a skunk at a wedding reception. Read through posts of the past and you'll understand why. Now, a couple or three questions.
Where are you located? Are you looking at heating only with no a/c, or both? What level of expertise is behind your heat load calcs? Is the ~10,000 Btuh per apartment total heat load at the minimum design temperature? How much of the heating season is at the design temp? Does the calc take into account the heat generated by every day living activities such as TVs, cooking, body heat, solar gain, etc.? If the 10,000 Btuh number is at the coldest temp of the year, and does not account for heat generated by life activities, you really only need to provide for peak demands. If that peak demand is only 3000 to 5000 Btuh, and only is needed 20% of the heating season, and most of the time you need only a couple thousand Btuh to keep the apartment warm, then maybe, contrary to what's been said, electric resistance makes sense. What's easy to overlook by everybody, is the fact that nearly all of the electricity that enters a living space gets converted to heat at nearly 100% conversion. This includes the electricity that goes into CFLs and LCD screens. You get 2 or more hot bodies, literally, in a small apartment doing a lot of cooking, surfing, reading, TV watching, whatever, you have a lot of heat being generated. In the past with poorly insulated, air leaky, homes this wasn't enough of a factor to make it worth considering. I can tell you from my own experience in my own nearly complete ICF house that human activity is a significant factor in a well insulated air tight home.
What you are looking at, on the face of it, is about 100,000 Btuh heat load for all apartments combined. That's enough to justify looking at heat pumps, gas boilers, individual in-wall heat pumps, or whatever. Especially you will want to explore geosource heat pumps. This is assuming you are willing to use a single heat source for all apartments combined. Another option is a mult-unit split system air to air heat pump. This is one outdoor unit serving several indoor units. Daikin and Mitsubishi are two I know of. Daikin has units that will provide heat down to 10F, or colder, outdoor temp. With 10 energy efficient apartments your primary heat load is probably going to be water heating. It makes sense to combine both domestic water heating and space heating into one heat supply as posters above have said.
Now, if you have done research and calculations that answer all my questions above, and you still believe that electric resistance heating for each apartment is the way to go, come back and ask again. You might get your original question answered based on experience of forum members.
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Building house - what a way to spend retirement! It's done! We're living in it! |
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Anne Andrews
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New Member
Posts:5
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| 02/03/2009 8:37 AM |
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Hello Hannah B,
We are a manufacturer of radiant heat film and have been for over 25 years. If you go to our web page www.calorique.com go to ceiling heating then scroll down to heat loss questions. Fill it in for each room and send it to me I will do a heat loss calculation for you and a quote. Then take that quote and compair to others. I believe you will find that your not going to spend as much on the radiant ceiling heat that is very, very efficiant. I will also be able to tell you what you will spend for the heat annually.
I hope to hear from you.
Calorique Radiant Heating. |
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BillN
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Posts:53
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| 02/07/2009 8:45 AM |
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From a building owner perspective, low installation cost and high operating cost is attractive, because it shifts the expense to the tenant.
This is the main reason why electric heat is used at all. An electric heating system, like baseboard, is a fraction of the cost to install over a hydronic system. If its a spec house, its a lot more money in the builders pocket when he sells it. The buyer usually doesn't realize the impact until the first winter.
In your case, if the dwelling units are that small, maybe a combination gas storage heater with a heat exchange coil for some in slab radiant will fit the bill. Since ist is low income housing, this is probably the cheapest radiant heat installation that you will find, other than electric.
That said, there are some places in the country where electric is cheap because of local hydro, or a co-op setup. I pay about $.12/kwh in NJ, NYC is closer to $.15. I have heard prices as low as $.04 per kwh.
The problem with a central system is that when a utility is "free" for a tenant, they will use it like pigs. Free heat= thermostat cranked all the way up with the windows open.
There are BTU meters that can measure heat flow. Check out this web site http://www.istec-corp.com/btu.html
If an apt had a single hydronic supply for hydronic baseboard or radiant, AND a small indirect for domestic, then the HOUSE can distribute the cost of energy based on usage.
Each unit could have 2 zone valves, dhw & space heat, metered at 1 point for each unit. In the case of radiant, each unit would need a pump, mixing valve, and a reset controller.
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Blueridge company
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Posts:211
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| 02/08/2009 1:28 PM |
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Yep the missing piece of information is location. This will address Baggers observation of what is green, Hydro is about as green as it gets less the fish kill. Coal is the worst at about 30% efficiency. Again to location, free heat means the door is open, further in places like NYC it can take up to a year to evict a bad tenant. If the unit is provided with free heat that can get very expensive. Isolated utility per apt means that the utility provider can lock off the heat. A land lord can not do that.
Small mod condensing units with demand domestic isolate the utility and are very efficient. a 10 pack will run about 5,000 per 1,000 sq unit in material. Electric boiler with a simple 40 gallon H20 unit will cut that in 1/2.
or if centralized heat is an option then modulating boiler with a simple pump manifold 1 per apt and pex in floor, flat panel radiators or wall mounted fan convector's are all good hydronic choices.
Again the missing piece is location/fuel/AC no AC/ budget or deluxe.
Dan |
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Dan
BlueRidgeCompany.com |
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