Self-Storage Meets Radiant Hydronic Heating:
The Long Term Energy Savings May Surprise You
BY RICHARD ZIMMERMAN
The Laws of Thermodynamics continue to challenge self-storage design
innovation. While relative humidity, condensation and traditional
forced air distribution systems are being reevaluated in the current
toxic mold and mildew environment, commercial hydronic radiant
heating has begun to see a wide acceptance within the U.S. and
European design communities as an alternative to forced-air heating
systems. As a result, today’s self-storage developers, owners and
operators are beginning to embrace radiant heating.
The Concept
Radiant systems circulate controlled high temperature water through
(BPEX) oxygen barrier crosslinked polyethylene tubing or (PEX)
polyethylene tubing, embedded directly in the concrete slab. Design
grids or zones provide controlled heating. Radiant heat eliminates
cold floors and the energy loss from forced hot air wasted at the
ceilings. The initial cost of a radiant heating system exceeds
forced air heating but is offset by reduced insulation requirements,
eliminating ducting and purlin roof structural framing. Radiant
systems are up to 40 percent more efficient than conventional
heating systems, according to the manufacturer and the Radiant Panel
Association.
Innovative Design Overview
Highland Hill Self-Storage LLC in Tacoma, Wash., opened in June of
2002. The design force behind this four-level, 98,000-square-foot,
704-unit development is Tacoma-based Tech-Fast Metal Systems, Inc.
While the initial design was for a three level facility on 1.5 acres
with a 24,500-square-foot footprint, local zoning restricted
mini-storage development. Adding to the complexity of the project,
soil testing revealed unstable conditions due to prior fill over
natural materials.
Developing this site was not easy, especially with record rain
showers forecasted for Tacoma as the construction window narrowed.
Given the regulatory zoning restrictions, the developer and general
contractor, Mountain Construction, applied for a conditional use
permit requesting 12 variances. Additionally, the natural materials
buried in the soil had to be removed and replaced. Amidst all of
this, focus shifted to a 24,500-square-foot basement opportunity.
The addition of a basement would increase the three level
development cost, while reducing the per unit expense. After an
extensive re-design, a basement prevailed over the site backfill.
Once the development team prevailed on all 12 Municipal variances,
permits were issued and construction began—just in time for record
Tacoma rainfall.
The basement dig became a pool of mud significantly impacting the
soil removal cost and construction scheduling. However, as the
basement footers took shape, the focus moved to the Radiant Heat
System, and non-corrosive BPEX tubing was laid out in temperature
controlled zones then attached to the structural rebar. The concrete
slab was then poured, enclosing the BPEX tubing and rebar in the
foundation.
For Radiant heat Systems, the BPEX tubing is attached to an energy
efficient boiler. For this project, the Janes Co., (the commercial
radiant flooring contractor), specified the Infloor Radiant Heating,
Inc. system and a Raypak Boiler with an 82 percent Annual Fuel
Utilization Efficiency (AFUE). Energy efficiency, cost, maintenance
expense and financial payback are all considerations in a boiler
specification. Energy Star rates energy efficient boilers (minimum
85 percent AFUE). Sunset Air, the HVAC sub-contractor, then designed
a single exhaust ventilation fan, fresh air make-up system,
incorporating air return shafts at each end of the building.
Utilizing the system, outside air is drawn from two louvered vents
located on each floor. The radiant floor efficiently heats the
outside fresh air as it enters the building. The air exchange system
is referred to as heat recovery ventilation. The systems continuous
operation draws air from each floor reducing odors and maintaining
indoor air relative humidity levels below 70 percent, avoiding toxic
molds and mildew contamination.
On this project, the proscriptive R-38 insulation code requirements
were reduced to R-19, six-inch roof insulation, based in part to the
radiant heating efficiency. The code variance resulted from the
component performance (u-value) analysis completed by Sunset Air.
The building exterior incorporated a seamed metal roof with a steel
panelized exterior wall on the second and third floors. The main
floor exterior wall was constructed of CMU, split-face, mortar-set,
rose-colored, masonry block (ASHRAE freestanding rated less than
R-4). With six inches of roof insulation, the first floor CMU wall
is rated at R-19.
According to the National Concrete Masonry Association, the mineral
aggregate and inorganic material in masonry block can’t sustain the
growth of mold or mildew. Split face, CMU block is widely used in
commercial construction for its esthetics, durability and mold/
mildew abatement. Omni Block has introduced a new CMU, insulated
(R-13.5 freestanding rated) split face, mortar set, masonry block.
This patented block system adds the option of insulation and sound
proofing to a commercial masonry specification.
Financial Feasibility Fundamentals
In the final evaluation of the energy efficiency of any building
system, the direct capitalization costs and operating expense
determine its feasibility. Traditional Cap Rate valuation can only
be used on facilities that have a stabilized net operating income.
Highland Hill opened for lease-up this June with only net operating
income projections. A closer look at the actual costs and the impact
of the radiant flooring presents a straightforward valuation method.
The total cost of the project was $4 million. The building cost was
$1million, or $10.00 per square foot. The radiant flooring system
cost was $125,000 or $1.25 per square foot. Compared to estimated
costs of forced air, gas heated systems at $.65-$.80 per square foot
for the common storage area and $3.50-$5.00 per square foot for the
office area. The additional radiant flooring expense would require a
5-year payback.
According to Dave Cook, CEO of Tech-Fast, the overall construction
costs as a result of the radiant flooring specification, resulted in
a 5 percent or $.50 per square foot building costs offset. The
radiant flooring capitalization cost is offset to $.75 per square
foot, competitive with forced air heating estimates and eliminating
any multi-year payback. The construction cost offset resulted from
the reduction of R-38 (10”) roofing insulation to R-19 (6”),
elimination of duct work and the resulting roof framing member (purlin)
structural reduction. The outside, make-up air ventilation system,
costing $18,000, would be required with either heating system, and
isn’t a factor in the overall feasibility. With an estimated 40
percent operational expense reduction compared to forced air heating
systems, the radiant system directly increases the Net Operating
Income (NOI) from day one.
The radiant system used for this project promotes energy efficiency
and the potential of ancillary income through a zoned heating
premium fee. The developer estimates that of the 75,000 square feet
available for lease, 25 percent of the tenants will pay a premium of
$.10 per square foot. This estimate would yield an additional
$1,875.00 per month or $22,500.00 yearly. In essence, while the cost
of the radiant heating system is higher than traditional heating, it
allows for a building design that costs less. That being equal, the
real benefit here is a long-term energy savings of 40 percent by
using radiant hydronic heat.
Resource Guide:
Tech-Fast Metal Systems, Inc.
(800) 709-4440
www.techfast.com
Mountain Construction
(253) 474-5281
www.mountainconst.com
The Janes Co.
(800) 974-5884
www.janes-co.com
Sunset Air
(360) 923-1244
www.sunsetair.com
Infloor Radiant Heating, Inc.
(800) 608-0562
www.infloor.com
Raypak
(800) 947-2975
www.raypak.com
Energy Star Boilers
(888) 782-2975
www.energystar.gov/products
Radiant Panel Association
(800) 660-7187
www.RPA-info.com
Omni Block
(480) 661-9009
www.omniblock.com
Toxic Mold & Mildew National Concrete Masonry Association
(703) 713-1900
www.ncma.org
Other Websites:
www.toxic-mold-news.com
www.themoldsource.com
Richard Zimmerman is a freelance writer and co-author of the City of
Scottsdale Green Building Program.
