|
|
|
The following text is from
a currently inactive and unfunded research project. We think that duct
losses are very significant and that some entity ought to undertake
further research in the area. To date we have not been able to pursuade
the CEC to fund it in the public interest.
Profitable
Residential HVAC Duct Sealing
Project Narrative
1 Project Goal
The goal of this project is to determine the feasibility of producing
an economically attractive residential HVAC duct sealing process.
2 Project Objectives - Detailed Discussion
of Objectives and Solutions
The technical objective of this project is to develop and test duct sealant
materials and a process that can be applied by a below average competency
HVAC technician or duct cleaner using ordinary tools. The intent of
the research design is to create a procedure that will become part of
his normal business practice.
Summary of Objectives:
We plan to explore a method of sealing ducts using blow-in sealant material,
delivering it cost effectively to the leaks so that it will remain stable
in the leaks in a benign way. Our research path will have four distinct
degrees of freedom:
-
Filler materials (we will use both “fluff” and “balloon/bubbles” filler
matrices as a starting set).
-
Bonding agents (expected to be water activated powders).
- Application sequence and
number of cycles (filler/mist/filler; or mist/filler/mist, etc).
- Sequence of different types/sizes
of filler materials.
These options will be explored rigorously, with the aim developing of
a cost effective, easy-to-use commercial product useable by HVAC and
duct cleaning technicians, with minimal or no additional training.
What: Method to be pursued
To accomplish this, we will develop a non-toxic, non-allergenic, easily
cleanable sealing process and filler material, which can
be blown down heterogeneous ducts. The filler material will lodge itself
in any cracks and holes encountered and seal them by clogging. The
blown-in filler clogging mass will be fixed with a vapor, which will
harden the material into the duct crack or hole. Once the first application
is allowed to harden, a second or third filler/fixative cycle may be
used. In the latter cycles flame- and biologic-suppressant chemicals
may be applied to suppress mold and bacteria growth on the fluff.
Significant consultation will be done with existing companies and materials
experts making “instant bubbles”(see Attachment I), “foam latex”, ”canned
string” and similar products for applicability. This may generate one
or more trips to visit with manufacturers of related products.
Materials
The materials to be used as “filler” can be classified into three distinct
groups:
-
Group
I materials: Cellulose dust will be used, with a
water activated surface finish glue as a “sticker”. Fire suppression
post-fixative will be required.
-
Group
II materials. Polystyrene dust, with an alcohol-activated
finish adhesive as a sticker. We will start by investigating very
lightweight polystyrene and iso-cynate based beads, that are impregnated
with helium in the field just prior to use, so that they are neutrally
buoyant in air for a brief period until the helium diffuses out (about
1 minute).
The beads can be delivered to the duct in a container that charges
them with helium. Helium is observed to be resident in expanded closed
cell polystyrene for a few minutes. Its outgassing and conductive
coating will be used to suppress the known electrostatic cling problem
of Polystyrene/Polycynene beads.
-
Group III materials.
Very small bubble/balloons, with a powdered water/casein based glue,
will be applied as a very fine mist. Attachment I to this proposal
shows a commercial bubble product that produces bubbles which feel
and act like soft, lightweight, small ping pong balls. For this material
research path, we will start with similar materials, and attempt to
use a helium bubble generator to make the bubbles neutrally buoyant
in air. The idea is to produce sealing “balloons in a can”. These
bubbles will be filled with helium, and a “sticker” surface treatment
will be applied as the small balloons are injected into the ducts.
Application Techniques:
The Float and Seal Approach
The eventual application procedure will be similar for the three materials.
The design goal will be to use equipment that is simple and profitable
for the HVAC technician to use. During application, the supply ducts
will be sealed where they enter the living areas. The normal supply
fan will be partially blocked or “plugged into” a variable speed drive
box, allowing the technician to use the existing house air distribution
fan for driving the system. This has multiple benefits:
-
It uses existing equipment familiar to the technician
-
Little
training is required, because fan pressure, fans, fan fuses and fan
controls are all part of a technician’s normal work.
-
Air flow/pressure
can be varied over a wide range, to accommodate large and small houses
with no equipment change.
-
Blowback
of materials to the fan area is suppressed.
Because some of the sealing material (whether balloons or fluff) will
escape, some will remain in the ducts, and some will enter the living
spaces both during the sealing process and later when it is released
inside the duct, the selected filler material must be non-allergenic,
non-toxic, non-staining, and easy to clean up. Easy cleaning is necessary
due to the nature of how the eventual product will be used, and is part
of the reason that current products are not being used. Some of the
sealant will blow out of the leaks before they are sealed, and as commonly
happens, some will flow into rooms when the room seals fall off during
use. This is not an infrequent occurrence with present methods, so
easy cleaning is a requirement of the fluff material design. At the
same time, the filler must bond to itself and the cracks in a cohesive
mass that will plug the leak. To effect this, we will provide and test
various water based surface chemistries that, when moistened with a
light mist, will bond the mass.
The three core material paths:
These starting materials will be designed to be airborne
and to plug leaks. Our research path will exercise these materials
as a starting point over a range of size (and possiblyHe gas) mixtures,
to see how they must be treated and modified to produce a viable economic
product. We will allow for changes in materials and material aggregate
sizes, as the tests indicate, to see what new properties are needed
to make them effective. Changes will always be towards efficacy, economy,
ease of use, and the idea that we are designing a product to best fit
the HVAC technician’s or duct cleaner’s toolkit.
We will test the above-mentioned materials and processes under Phase I
in a series of test chambers at the Davis Collaborative lab. From our
experience with duct sealing, the basic test set-up is straightforward
– cleaning is not.
Description of the Test Duct Races:
“Race I” is a fan-driven duct, with pressure and flow gauges, and a socket
end capable of taking a set of interchangeable “standard” leaky ducts.
The race has pressure gauges and a long straight section for flow measurements,
as well as allowing the simulation of a long duct length to the leak.
Identical “Standard” metal sections are used for testing leaks, with
a standard set of holes and cracks. This allows for accurate repeatable
comparison of different materials. The test ducts are metal, so cleaning
and standardized filth can be added each time.
“Race II” also a fan driven duct, but open for testing a wide array of
materials. In this field test set-up, we will try to seal all duct
types and ad hoc mixtures
of flex-duct, fiberglass duct, and metal, so we can look at how different
materials interact with the different sealants and processes. We will
be focusing on materials used in California construction that are primarily
engineered for cooling as opposed to heating dusts for the north-eastern
US.
The facility allows for testing both clean and dirty ducts. This test
facility will be constructed so that tests can be repeated with different
pressures, fluff materials, and surface bonding agents, and with different
degrees of cleanliness in different types of cracks.
In the Race I standard ducts, with a large number of punches and replaceable
duct pieces, this testing is standardized and is repeatable when clean.
We will measure flow and pressure as the sealant is applied. The sealing
effectiveness will be judged in several ways:
- Sealing effectiveness: the change in flow for a given pressure
- Ability to bridge different shaped standardized leakage gaps
- Response to dirty surfaces
- Response to a calibrated shock (hitting) of the duct to judge adhesion.
- East of application and clean-up
- Time of application
- Ease of cleaning duct after application as well as
- Robustness to physical duct expansion and contraction (elasticity)
2 Energy Problem Targeted: Leaky HVAC Ducts
In the United States, HVAC air ducts are a major source of leakage of
both cold air from air conditioning and hot air from heating. Typically,
20% of the energy in a home HVAC system is lost to duct leakage. Indications
are that the problem is similar, or more severe, in commercial establishments.
There is only one commercial solution for resealing ducts in residences.
Unfortunately, it is too expensive for use in most cases, and exists
primarily as the result of utility subsidy or legislative programs.
3.a Impact on Energy Problem
Adoption of duct sealing as a standard marketable service by the HVAC
service industry and/or the duct cleaning industry will dramatically
reduce air duct losses and save large amounts of energy all over California.
There is also a health issue, because the duct leakage we are referring
to is on the supply side of the delivery system. With leaks on this
side, the house becomes depressurized. The depressurized house sucks
air in from garages, moldy walls and cracks, down gas flues, and other
locations. Leaks on the return side have a differential effect depending
on which air is drawn into the leak. The duct sealing technology addressed
here is for the supply side, where almost all of the hidden leakage
occurs.
If we could cut leakage by half on average by sealing ducts tightly, we
should be able to save about 10 % of the energy used in California for
heating and cooling residences. The sealing would be done to a much
higher standard than 10%, but we must average the effect over time.
3.b Benefit to California Electric Market
The direct impacts will be seen during the heating and cooling seasons.
In either case, conditioned air comes from the furnace/evaporator coils
into the house. In winter, the furnace will have to run less often,
saving electricity. In summer, where the big impact for the California
Electric market is, the impact will be dramatic for houses that have
their ducts sealed. If in the summer a house spends 60% of its electricity
bill on air conditioning, a 20% reduction would exceed a 10% electric
energy savings directly for that consumer, and because marginal losses
are very high in the summer, the marginal system savings
(including losses) would be over 12% of electric demand savings. In
addition to the energy reduction, with the demand reduction there will
be a decrease in price through market elasticity. As the demand drops,
so too does the price, historically rather dramatically in the summer.
What this will be in the future is pure speculation, but it is unlikely
that the price elasticity would be less than the marginal electrical
loss rate. Thus, the price per kWh decrease will be in the 20% reduction
range from a 10% fall in electrical energy, giving about a 28% total
cost savings to the aggregate
California consumer.
4 State of the Art
4.a Results of Literature Search
Considerable related research has been done at Lawrence Berkeley Laboratory
over the past 20 years on ducts and sealing ducts. LBL reports point
out that over 20% of heating and cooling energy is lost due to duct
leakage. These reports are located at: http://www.lbl.gov/Science-Articles/Research-Review/Highlights/1998/EES_duct.html
Their reports document the pervasiveness of the problem. They document
their test facilities, and the development of Aeroseal – their licensed
commercial duct sealant. The complete list of all Aeroseal background
information is available at this web site
http://epb1.lbl.gov/aerosol/pub.htm#GP
Some of the key papers are as follows:
-
Carrie, F.R. and Modera, M.P. (1993) "Particle Deposition in a Two-Dimensional Slot from
a Transverse Stream", Lawrence Berkeley Laboratory
Report. Presented at the 12th Annual Meeting, American Association
for Aerosol Research, Oak Brook, Illinois, October 1993.
-
Carrie, F.R., and Modera, M.P., (1995) "Reducing the Permeability of Residential Duct Systems",
Presented at the 16th AIVC Conference, Palm Springs, CA, September
1995.
-
Modera, M.P., Dickerhoff, D.J., Nilssen, O., Duquette H., and
Geyselaers, J. "Residential
Field Testing of an Aerosol-Based Technology for Sealing Ductwork."
Proceedings of ACEEE Summer Study, Pacific Grove, CA, August 1996,
The LBL duct testing lab has been less active during the past 5 years.
There is considerable research in sealing of ducts, but the research
emphasis has been on duct tapes and duct sealant that is hand applied.
This sealant is inappropriate for an aerosol application.
4.b Comparison of Existing Products
Small residential and small commercial air duct leaks can now be plugged
using simple procedures that blow sealants (to be developed in this
research) down the ducts until they block a leakage hole. The process
is slow, bulky, requires special equipment, significant training, large
capital investment, and a franchise from Carrier. It is not part of
an HVAC technician’s or duct cleaner’s normal service set.
This proposal will examine coarser, lighter sealant materials than are
currently used and will explore chemically fix the material into the
orifices. The efficacy of the existing, somewhat similar, technique
using very fine particulate “sticky” material” has already been proven
in the field by Aeroseal, now a subsidiary of Carrier. However, the
Aeroseal process is seldom cost-effective in existing housing
due to the expense, filth, training, slowness of application (which can take several hours) and special
computer controlled equipment required.
This research will find a new airborne sealant and sealant technology
marketable by the HVAC repair and duct cleaning industries. To be economically
attractive, it must be simple, cost effective, easy to apply, and most
importantly, it must be usable by normal HVAC or duct cleaning technicians with little training or required equipment.
5 Feasibility Issues:
Feasibility is determined by market acceptance. There is little question
that some sealants can be blown down ducts to seal them. The question
is whether a product can be developed that will gain widespread market
acceptance: The product characteristics that determine this feasibility
include:
These are the feasibility issues. LBL has explored a very narrow set
of materials (1), and has come up with a good solution that has met
with only limited market acceptance, thus a new product is needed.
6 Proposed Innovations
-
Using
a multi step process air system to seal ducts.
-
Using
existing furnace fans with speed controllers (small vfd if needed)
as blowers so no special equipment is needed.
-
Inducing
sealant through a 0.25” pilot hole in a primary distribution plenum.
-
Possibly
using “as light as air” gas/solid materials
-
Separately
using moisture as an activator of the bonding agent to product composite
sealant.
7 Primary Tasks
Task 1. Administration and Reporting
-
Task 1.0 Kick-off and contract adjustments as/if directed
by DOE.
-
Task 1.1 Adjustment of schedule to match funding release.
-
Task 1.2 Set up accounting and invoicing procedures as
directed.
-
Task 1.3 Monthly reporting as needed by DOE.
Task II Material Review and Collection
The current plan is to start with three different material types, and
to use a series of dry surface bonding agents. In Task II we will exhaustively
look at our selected materials and discuss these with people in the
textile, industrial hygiene, and HVAC industry to explore the issues
of fire, mold, bacterial growth, short term stability, longer term durability,
deterioration under thermal cycling, and other selection issues.
Task III
Set-Up and calibrate
In this task, we will construct the test ducts and plenums, and connect
them to our pressure and flow instruments. We will review materials
and test bench calibration. The Davis Collaborative has the equipment
necessary for testing clean and dirty ducts with pressure and flow gauges.
The Data Acquisition System (DAS) system will be upgraded and automated
for these tests. Because it is expected that there will be many hundreds
of minor variations in procedures, sealant types, coatings, and treatment
sequences, the DAS will be complemented and integrated by a significant
data logging and data management system.
Task IV Testing
-
Task IV a - “The Primary Races”.
There will be at least two different duct testing set-ups, using duct
board, flexduct, and steel. Primary testing will be done on what
is called “Race I & II”. These races will have a series of identical
blind sections with small orifices cut in them. These standardized
metal leakage slots and holes will be the same in multiple replaceable
sections. This is necessary for standardization, and because the
replaceable sections with the standard holes will get “gummed up”
and need to be carefully cleaned out between tests. Extensive cleaning
and repeated measures is required for quantitative testing.
-
Task IVb - “The Field Test” – in Race III”
When we have narrowed the field to a few working material/process combinations,
we will try them on other common duct materials. All that is established
with Races I & II (with the standard steel leak orifices) is which
materials/bonding agents/process work on sheet metal, with different
types of dirt. Gaps in duct board, whether faced or not, are quite
different in that the breaches are larger due to poor joint mating
and failed tape. Likewise, gaps, tears, rodent holes and punctures
are equally different in very thin walled flexing plastic flexduct.
8 Market Connection
This research is driven by observing that the market is not responding
to a particular product for a set of reasons. We are addressing those
reasons through research. We are knowledgeable about them because we
have interviewed many HVAC contractors who are familiar with the Aeroseal
product, and are HVAC contractors ourselves.
In terms of manufacturing the product after product development, it would
have to be shown to be safe on numerous counts, and tested in the field
with independent HVAC contractors. This would be a follow-on process,
unrelated to this research.
Footnotes
|