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Radiant Floor Heating

Project: Owner/built 4,200ft2 (390m2) renovation/new construction of a private residence.

See this page for budgeting HVAC design fees.

Click on thumbnails below for larger images.

Figure 1. Old mechanical room during demolition. Boiler, solar DHW tank and air handler and a few circulators were refurbished and used in the new mechanical room.

Figure 1a. Original basement during demolition stage.

Figure 1b. Original home pre demolition (east side). Right hand side foundation served the right hand side new construction shown in Figure 12.

Figure 1c. Original home pre demolition (west side facing downtown Calgary). Note solar collectors; and basement windows for reference in Figure 13.

Figure 2. Wall detail #1, metal seam siding on 2" Roxul on Tyvek on plywood on studs

Figure 3. Wall detail #2, IPE wood on strapping on felt on Tyvek on plywood on studs.

Figure 4. East facing foyer framing.

Figure 5. West facing view glazing. This room primarily heated with radiant floors and a second stage of heat from the air handler during peak loads.

Figure 6. Radiant heated north wall of the foyer. This and another radiant wall (Figure 8) plus radiant floors serve as the primary heating for this space with a second stage served by the air handler for peak heating loads (see Figure 7 below).

Figure 7. Radiant heated north wall of the foyer. showing second stage air outlet.

Figure 8. Finished radiant heated north wall of the east side foyer. Picture taken from inside the foyer facing north and looking up.

Figure 9. East facing radiant heated wall of the foyer. Picture taken from inside entrance looking up and to the left.

Figure 10. Finished east facing radiant heated wall of the foyer. Picture taken from inside entrance looking up and to the left.

Figure 11. West view overlooking downtown Calgary. Due to the high window/wall ratio this room heated with radiant floors and walls to keep the fluid temperature down to ensure maximum efficiency from the boiler.

Figure 11a. Make up air location #1 for kitchen range hood. Second location for make up air is from floor and wall registers in living room and foyer respectively.

Figure 11b. High capacity kitchen range hood.

Figure 11c. Rendering of the north and west walls.
Credit: Nyhoff Architecture


Why I specify non electric thermostatic room controls.

Still the worlds most perfect thermostat (IMHO)...

The non-electric thermostatic controller valve was invented over 70 years ago and its simplistic design is just as reliable today as it was back in the day.

A few features:

*It has no power
*Batteries not required
*Self powered 
*Was the first wireless stat
*Is fully modulating
*Senses operative temp.
*One (1) page IOM manual
*Works like a door knob
*Turn right for less heat
*Turn left for more heat
*Incredibly reliable
*Anyone can work it
*Stocked everywhere
*Perfect for reduced:
 - manual dexterity
 - visual acuity
 - cognitive abilities

Perfect for grumpy designers and their clients who are sick and tired of technology stealing away valuable fishing time!

Computer modelling of solar dump using finite element analysis (FEA).

Due to the output of solar collectors and associated systems, it is sometimes necessary to "dump" the excess heat. In this case we had the controls divert solar flow to an underground loop when ever the storage tank reached 190F(88C).

Using flexPDE we set up a model to help us understand the pipe/earth heat exchanger necessary to cool the solar flow when the heat was not needed.

The following two images are screen shots from the program outputs.

For other use of the FEA tool see our work on under slab insulation and wall insulations.

Though there are many radiant design software programs available, we use our own spreadsheets based on the ASHRAE Handbooks.

Screen shot for the radiant design summary.





Featured Residential Project
Copyright (c) 2014, Robert Bean, R.E.T., P.L.(Eng.), and content contributors

Featured Commercial/Industrial Project

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Design services: drawings and specifications examples:
Sample #1: drawings and specifications for an owner built infill project
Sample #2: drawings and specifications for an owner built gut/renovation project
Sample #3: drawings and specifications for an owner built project
Sample #4: drawings and specifications for  an owner built project


This particular project started in fall of 2012 was an owner-built 4,200ft2 (390m2) in-fill/new construction of a private residence in Calgary, Alberta; space heating operating temperature is 115F (49C) at outdoor temperature of -40F/C, approximately 10F(6C) lower than calculations. A subsequent blower door test showed an ACH50 of 1.6 compared to typical new homes of 4ACH50 to 4.5ACH50. 1.6ACH50 (EQLA=89.9in2) is on par with Canada's R2000 High Performance Housing Program.

The old home (Figure 1 to 1c) was torn down with the exception of the foundation and grade level subfloor. The original mechanical was hydronic radiant floors with a fan/coil and solar domestic hot water. The owner wanted to reuse as much of the old system as possible; the boiler, storage tank, solar system and a few components such as circulators were refurbished for the new system.

The new essentially maintenance free building enclosure (see Figure 12) is a higher performing assembly with a combination of spray foam and friction fit batt insulation in the stud and joist cavities, and external insulation as shown in Figure 2. The exterior finishes is metal seam siding and IPE wood. All windows were triple pane argon filled low E glass.

Inline with the owners objectives was a few features such as the clearstory foyer (Figure 17) on the east side, and west side views of the city (Figure 11 and 13).

North and south neighbouring sides have very little glass less 5% window/wall ratio. Also the owners did not want to use forced air for the primary systems; as such a hybrid radiant based HVAC system was incorporated into the new building.

There are a number of feature considerations that had to be incorporated into the design, specifically was the high volume kitchen range hood (Figure 11b) in the presence of two wood burning stoves. To prevent negative pressure from occurring during operation of the kitchen range hood a 100% make up air unit was used (Figure 25) with the control sequence opening first the outdoor air damper, then second by turning on the make up air unit which trigger the operation of the kitchen range hood.

Also we developed a FEA tool to help design the ground based solar dump to handle the excess heat generated by the collector during low load periods.

Figure 12. Street view (east facing). Note the refurbished solar collector on top elevation. Solar is primarily for domestic hot water but also charges the tank for space heating. Solar dump circuit is a copper line under the garage slab. Venting for bathrooms, kitchen range hood and boiler on north side.

Figure 13. Yard view (west facing over looking downtown Calgary). Note the solar collector on top roof. Also on this side at main floor level is outdoor air intakes for make up air unit for kitchen range hood plus intake and exhaust for HRV. For reference make note of the two basement windows (left side of image) from original foundation in Figure 1c. Upper level, north and south walls have no glass and have radiant heating in addition to the heated floors. This extra radiant area was done to ensure low water temperatures in a somewhat higher load area to enable maximum boiler efficiency.

Figure 14. Street view (south facing). On the inside of the exterior wood finished wall areas are heated shower walls (see Figure 15 below).

Figure 15a. Inside view of master bath heated shower wall rough-in. See 15b for finished product.

Figure 15b. Inside view of master bath heated shower wall. Natural light provided from privacy window (typical of two showers).

Figure 16. Towel warmer in master bathroom (typical of all bathrooms).

Figure 17. Triple pane argon filled glazing is excellent however with this wall/window ratio it will still contribute to both a high solar load during the morning and a high heating load during non solar periods at design conditions. This high heating load results in a drop of the inside glass surface which increase the convective flow in the space (downdraft) leading to thermal discomfort. To compensate for the heating load the floor is heated as well as the two walls visible in the picture. Note: the temperature of the walls and the resulting radiant energy is in the long wave range; translation...the glass becomes opaque to the energy so it absorbs it. The result is the glass heats up rather than let the radiant energy pass through. This reduces the down draft effect from cold glass which improves thermal comfort in an otherwise very difficult area to heat (see here for radiant theory). Also it is possible with some control reconfiguration to use the walls as solar collectors for heating in the winter and/or for cooling the space.

As a matter of interest, at the time of the photo (appx 1:00pm MST, Dec. 23) the outside cladding during the solar load was well over 110F(43C) at 0F(-18C). After the morning sun, this conducted through to an inside surface temperature of approximately 80F(27C) resulting in a room temperature of 75F(24C). Translation: the inside surfaces of the foyer became a radiator. The owner has manually operated side panes to relive the room if conditions warrant.

This differential (between outside cladding and inside finish) was severe enough to cause sufficient expansion of the original pane of door glass to expand to the point of distorting the exterior finish. The vendor ultimately replaced it with multiple pieces as shown.

For the snipers in our readership, even though the building tripled in size and the ventilation load increased dramatically with the range hood, the refurbished boiler was used without upsizing. This is due in part to the high performance characteristics for much of the enclosure.

Figure 18. Simple non-electric thermostatic controls for the floor and wall heating. See sidebar as to why I love these devices. I specify these on all projects and do my best to prevent clients from using anything complicated. Sometimes the client wants fancy thermostats but we always prepare them for the issues due to their inherently unfriendly features.

Figure 19. Piping schematic for boiler room. This one of 13 pages (typical) of details we produce on residential projects (see full set).

Figure 20. Piping and control schematic for zones and heat terminal units (HTU's).

Figure 21. Radiant tube and manifold layout for main floor and second floor.

Figure 22. Duct layout for make up air and second stage heating.

Figure 23a. Upper loft radiant wall, south facing - spray foamed and friction filled. Plywood backing and radiant tracking installed as per Figure 23b.

Figure 23b. Radiant wall tube layout for upper loft (one of two heated walls for this space). See Figure 11 and 13 for reference.

Figure 23c. Finished radiant wall for upper loft. See Figure 11 and 13 for reference.

Figure 24. John Wiehler from Wiehler Mechanical Ltd, Calgary, Ab. (403) 277-6970. John and his guys had to incorporate the old with the new while still meeting the clients budget for a Grade A Indoor Climate Systems.

Figure 25. Existing air handler provides second stage heat for the foyer and living room plus make up air for the kitchen range hood (see Figure 11a and 11b).

Figure 26. New HRV for upper floor bedrooms and bathrooms.

Figure 27. Outdoor air intakes for the make up air unit (Figure 25) and HRV (Figure 26) in the foreground. In the background is the HRV exhaust air from bedrooms and bathrooms.

Figure 28. Combustion air intake and exhaust air outlet for the refurbished high efficiency boiler (north wall).

Figure 29. From upper elevation down and to the right; refurbished solar collector, exhaust vent for existing wood burning stove #2 in den, and new kitchen exhaust vent hood.

You are most welcome to email us to see if our design schedule fits with your build schedule. At the very least we can provide you with an hourly telephone consult to help you plan your next project.

Sample Projects:

Sample #1: drawings and specifications for an infill project in Calgary, Alberta, Canada.
Sample #2: drawings and specifications for a gut and renovation project, Calgary, Alberta, Canada.
Sample #3: drawings and specifications for a new build project, Rocky Mountain House, Alberta, Canada.
Sample #4: drawings and specifications for a new build project, Michigan, USA

For additional support on this topic visit our visitor services page.

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