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Forums | Energy Efficiency | In floor heating requirements |
| Author | Message |
bcroft1 | Posted - 20 December 2002 10:47    I am planning for the construction of an ICF house in Southern Alberta. The house will have finished concrete with in floor heating as well as incorporating some solar aspects (south facing, optimum glazing, etc.). Everthing I have read regarding heating systems for ICF houses suggests that the system can be reduced as much as 50% compared to a conventional home. Can the same theory be applied to an in-floor system when coupled with solar aspects? By reduction I guess I mean the water tank supply system.Do I need a boiler or will a standard hot water tank do? The local dealers of such systems say the boiler is necessary. I'm wondering if this is another case of people not understanding ICF housing. Perhaps it's me. |
dyoungkeit1 | Posted - 18 March 1999 22:13 You havn't read enough yet. In your decision making, consider that you are also choosing whether or not to have filtered and circulating air. The energy required to circulate the hot water is comparable to the fan energy of some other system. The measurable quantity of heat your house requires is far more than your domestic hot water tank can produce. If you can not measure your heating requirements, find a friend who can, or learn how to do it on the internet, BTU/hr loss formulae are there.A person with average math background can do it. You must know what materials are in your wall and ceiling for insulation, your window sizes and types, and a lot of other measurements. When you get the grand total, you will know what BTU/hr size to buy to make up for the calculated loss. Dean Youngkeit 21 North 100 East Willard, Utah 84340-0041 (435) 734-0681 youngkeit@brigham.net |
dwilson | Posted - 19 March 1999 1:9 Depending on roof and window details, ICF houses must have very little infiltration compared to traditional framing methods, which typically have about 50% (roughly) of the heat loss from infiltration. I can intuitively see how the 50% claim could be made. In addition, radiant floor heating systems conservatively claim 15% (and often more, in reality) energy savings over conventional heating systems. There is no stratification of hot air near the ceiling (or roof, which is exposed to outside temperatures), and convective losses and stack effect are both reduced. Your average sized home can use two or three small wet rotor circulators which can draw as little as 0.4 amps to 0.75 amps each, whereas forced air blowers use about 6 amps. Radiant floor heating in concrete with no floor covering is about as efficient as it gets, the water circulating in the slabs can be as low as 90°F. Solar gain can result in room temperature overshoot in high mass radiant floors. The slab which is already at 85°F will likely overheat quickly from solar gain. To compensate for this, a "smart" control should be used, one with Proportional Integral Derivative (PID) control logic. It measures how big the difference is between setpoint and room temperature, how quickly it is changing, and how long it has been occurring. It then adjusts system water temperature accordingly. It is imperative that you have a control that can compensate for solar gain. Outdoor reset controls sense outdoor temperature and adjust system water temperature accordingly. The colder it gets outside, the warmer the system water, and vice versa. This also helps, it's like cruise control rather than on/off response. Tekmar Control Systems in Vernon, B.C. makes state of the art controls that provide all of the above features. The basic formula for heat loss is Q=U*A*delta T, where Q=btu/hr conductive heat loss, U=conductivity of the building material (the inverse of additive R values), A=area of surface exposed to outside temperatures, delta T=temperature difference between outside temperature and inside temperature at design conditions. Loss through the floor is a bit different, depending on amount of slab edge exposed, ambient ground temperature, insulation below slab, and other factors. Get a GOOD book on the subject. John Siegenthaler's "Modern Hydronic Heating", Delmar Publishers, ISBN 0-8273-6595-0 is as good as it gets. Water heaters typically have inputs of 30 to 50 thousand btu/hr. Derate for appliance efficiency and altitude, and you may end up with a btu output that's 60% of the input, not enough to heat your average home. Additionally, there may be building code issues with using an appliance to do something it's not designed for. Additional safety devices will have to be added. High output commercial water heaters or multiple hot water heaters could be an option. Your starting point is to determine your home's heat loss. |
dyoungkeit1 | Posted - 7 April 1999 13:38 The previous author is 100% correct in his statements. There is an oversight. There is no stratification, but there is no air movement for filtration nor dispersal of new material emmisions that cause the "new house syndrome" disease. The Paul Harvey radio news sponsers a room air filter capable of solving this problem in local parts of the house. |