We just bought a house recently its aboiut 25 years old and needless to say
has a lot of work TBD.
We've discovered mice/rat droppings in the house and I am terrified that
they are living in the ducts. I am working on an comprehensive pest
elimination program (the pest control companies I spoke to just tried to
seel me a plan to come back and poison bait the rodents). but all I've read
indicates that we have to be really pro-active in this.
My question is this: once I have eliminated the current infestation and
reasonably fortified ourselves against further ones, can I just wipe out
the ducts with a 10% bleach moistened rag ?
Our ducts are metal but I dont know if it has fibreglass inside it- is
there anyway to tell ?
I talked to some duct cleaning companies and they just said they would
vaccum it out, but the literature on hanta virus says that to NOT vaccum
the droppings of which I imagine there is truckloads in the ducts!
Any ideas on what I should do about the potential of mice living/droppings
in the ducts ?
Is there some tool/device that I can buy/rent out to look into these
Do a GOOGLE for asthma + mouse + urine
It can be a serious problem and not to be
If the ducts are unlined (plain sheet steel)
you can pull a heavy wad of rag (big towels)
thru using a snake (fishtape). Use whatever
disinfectant is recommended.
I would be surprised though if mice are actually
living in the ducts. Commuting, maybe.
More likely they have built tunnels in the
insulation (walls/ceilings). If you can
poison them, the bodies dessicate pretty rapidly.
The $64 question though is: HOW are they getting *in*?
Unless you solve that, everything else is a waste
of time. Takes a lot of detective work to find
the tiny openings they can squeeze in thru.
Do some more GOOGLing for mouse infestation or similar.
Do an Advanced search:
on this ng for "mice" or "mouse".
There should be dozens of past threads discussing it.
If you're not allergic to cats, a couple of them will
You'll never get the ducts cleaned, not by any method. Using rags and trying
to pull them through is an exercise in frustration (your rags will snag on
every screw, assuming your ducts are screwed together) and you'll never
really get them clean. Duct cleaning companies that would do a thorough job
would most likely cost almost as much as a new duct system ...
That would be quite interesting...mice in a sealed system....IF its still
You could, altho, it wont do much.
Seriously...you look inside them.
Duct cleaning, in most cases, is a total scam.
If the ducts are that bad, for whatever reason the correct method is to
Call a qualified HVAC company out to evaluate your situation.
The Inspector runs about $2500 for the good model. I do not know of anyplace
renting these as the company does not want them in the hands of non trained
persons outside of the HVR trade.
Normally, if your system is complete, and not in need of repair, there is no
way for mice, or any other critter to get into the duct system, or your
heating/cooling unit. IF they are, there are other issues to worry about.
The ONLY ones I have seen that have critters in them, are ones that either a
panel door was off of, or one that had flex duct touching the ground. and
the animals had torn through it.
Duct cleaning is a scam most of the time. Lots of people want it, thinking
its a good thing, and the companies make it look so wonderful and such..but
its rare, and I mean RARE that you need it. If the system is in good working
order and been taken care of properly, the supply ductss should be clean,
there should be no mice or rats or snakes or coons running in the
duct...being that yours are metal, and probably not insulated on the inside
you would hear them running around and it would be amplified.
I would call a qualified HVAC company out..have them evaluate your
situation, go ahead and have your system serviced completely, meaning a
complete coil flush and check things like the condition of the duct, unit,
etc and if you are still worried about viri and such, get a quote for a new
duct system, AND a set of UV-C band lamps installed in the ductwork to kill
anything that might be in the airstream.
Talking about any HVAC system in any home..
it should be sealed from the return, to the supplys....if not, its not
If its square duct, its also held in place with a pitsbugh cleat or other
form of rolled edge.
If they are round, they are prob not insulated on the inside, since you just
described duct wrap insulated duct.
I would not even do that. IF a customer called, and wanted to know, its
real simple, a roll of UL181AB tape, a section of sheetmetal, a snip, and
some screws and mastic..
Cut a small hole in the middle, insert the lens, or look on the BACK side of
the section I just removed...its either insulated or not, patch the hole,
hold in place with a couple of screws, tape over it, mastic the tape, put a
new section of insulation in, and tape and mastic it.
That way, you know without a doubt what you are messing with.
Fiberglass dust? Umm...its been ruled out as a carcenogen. So thats not a
worry, altho, I refuse to use duct that has insulation on the inside, or
ductboard type ducts.
You are not wasting a contractors time. If you just bought the home, hes the
guy you want out there anyway, since you should go ahead and have the system
cleaned, and serviced.
No telling when the previous owners did, and if you have one you have used
before, he should tell you about the ducts for nothing.
To me its not.
I love the cleaning companies...they make us lots of money when we get
called out to fix the things they destroy.
I had a customer call me one time and said that a local company removed over
30lbs of dirt from her ducts and wanted to know why...
it was the insulation from a section of old duct they got...
If I wanted to retire in a couple of years, I would start a duct cleaning
company...or add it to ours.
Again....the actual need for such is so minute, its not worth it.
$300 or more for one that you can actually use..
Ive looked at the cheapos .....real nice (sarcasm here) views....
UL181A-B tape and a bucket of mastic....thats what you need.
We install them in all the new installs that are 14 SEER or higher, and if
the customer wants them in a low end system, thats fine too.
I have two on my home, and its more than paid for itself.
We use the UltraVation models now, due to the incredible warranty on them.
I was using one company, but they didnt like us selling them direct to
homeowners, so we dropped them, but still buy parts for the customrs we
service and bought from us.
I am assuming u are talking abt my type. :) Anyway when we bought the
house a couple of registers were off and to the side, and who knows what
the previous owners did.
Two problems with that-1) I dont know how to remove metal the ducts,
they are covered with insulation batting and some kind of plastic
sheeting over it held together with duct tape.
2) I would not know fibreglass interior insulation if it hit me in the
head. If I can somehow see inside the ducts, ( not just the ends of the
duct where the registers are) and it looks like metal I guess I could
assume its all metal everywhere. Here is another thought maybe I could
clang something inside it and see if it is metallic sounding or a dull
thud. If it has fibreglass interior insulation how thick is is typically
? So I can figure out if its useful at all to try a sound test.
I am calling around looking for HVAC contractors but I dont want to
waste their time or mine if it is metal ducts because I know I can clean
them as far as possible without worrying about fibreglass dust.
Yep read the EPA stuff on it, the jury is still out on that it seems,
besides I've read some the experiences of ppl here - about not
disturbing anything too deep in there....
What about some cheapo fibreoptic scope ? It would be a fun thing to
I've gotten a lot of hardware cloth, screws etc., getting ready to find
and seal em entry points, I just want to be SURE. I really dislike the
thought of unknown mice/rats running around in my house. I dont so much
mind the known ones (ie., pets which we dont have or intend to). Just so
that those mouse fanciers out there know that this is an issue of
territoriality. I digress.
I had not heard of that one -sounds very interesting. While I believe an
occasional flu and cough/cold etc., keeps ones immune system buzy,
things like HANTA/corona virus/sin nombre and various other
unpronouncibles scare the daylights out of me.
Well..its a plus, but not needed.
When I say sealed, imagine this..
You have a central return, and for the sake of arguement, thats the start of
the airflow to the unit, back into the home, (technically, it is)
What I mean by sealed is:
Return filter grill is set into the return box. The return box has had all
seams and connections sealed with mastic, and even the filter grille itself
may be calked around all 4 corners...some higher end homes have this done to
insure that no air is being pulled around the filter.
The duct, metal, or flex, or even that crappy fiberboard, is sealed at the
start collar, or take off on the box, with tape, and mastic. All joints, if
metal where the duct is connected is sealed and mastic on top of that. The
connection to the furnace, or air handler as the case may be is also sealed
and mastic added. All doors and access plates on the furnace or air filter
are in place and all screws holding them in place are there.
In the case of a furnace, with AC added, the AC coil is sealed to the
furnace with tape and mastic, with all mounting screws in place. The supply
duct, be it metal, flex, or ductboard is also taped to the take off and all
joints are sealed.
Every room supply feeding off the main trunk line, is sealed with mastic at
the very least at each take off joint and any and all joints leading to the
supply boot is sealed. Where the boot comes into the home, be it the floor,
or ceiling, the area around the boot is sealed with either caulk, or
silicone. The register is in place...this keeps indoor critters from being
inside the AC critters, unless they are tiny mice and you have large
openings in the grilles, altho its been said that a mouse can get into a
hole smaller than a dime...believe it.
All kinds of stuff normally fall into the ducts over time. When I went to
clean my return trunk and return lines (I have a return in each room of the
home) I found toys and all kinds of things that had fallen in over time and
since there had been no children in this home since the 50s..you can imagine
how long they had been there with no problems.
When we go out to replace a duct system, normally the majority of the
garbage in the ducts can be found withing arms reach of the register boot.
Worst case we ran into was a kitchen duct that was literally filled with
roaches. Real fun...
Cant see it from here, but sounds like the 90 might have come apart and you
are feeling the ductwrap...not sure...have it checked.
If you go back all metal, you can expect a high price. Remember something
If you are going to do this, and your current heating and cooling system in
the home is over 15 years old, dont bother doing the ducts, unless you go
ahead and get a new system unless the ducts are just totally crap.
The duct system is part of the cooling and heating system, matched to the
unit. If you have to go later and replace the furnace, you MIGHT find that
you have to replace the ducts too.
any legitimate contractor that you call out to price out a system for you
will perform what is called a manual J, (*T* in the case of a heat pump)
that is a load calculation based on the construction of the home that takes
into account many different things. What was right 20 years ago, with todays
equipment might not be right today, or the unit you have now was never sized
to be correct for the home. In addition to this J, or T calculation, they
must do what is called a manual D duct size calculation. In a nutshell, what
this is for is to insure that each room has enough airflow to supply the
proper heating BTUS and airflow to each room for cooling.
The joke around here with contractors like myself that ACTUALLY do this work
But...EVERY take off is 6 inch..right?
Some rooms might be 6 inch, some might be 4, like a bathroom, or closet area
that needs to be heated and cooled, or they might be 7, or 8 or larger to
insure that the system is working right, and if you get the ducts replaced,
INSIST that the installers place balance take-offs on the system so that you
do not have to rely on the registers to control the airflow...many times,
you may be geting too much flow to one room, and not enough to another, even
after a manual D and the installers can control that, lock the balance in
place and you dont have to worry about it again.
Flex duct....its cheaper, its frowned upon by some, but its legal and works
great provided its a quality made duct and it DOES remove much of the noise
that most metal duct systems tend to have to a degree.
It also MUST be sized correctly, and supported per its instructions. Its
fast, its easy to seal, and the right crew can put in an entire system in
under a day.
Metal will vary literally on the time you place the order. Most tin shops
are now only making promises to hold the quoted price for a few days due to
the rising and falling almost daily price of sheetmetal.
I have done some for as little as $900 for a small non complicated home with
what some would call a spider web of duct, to several thousand...most
expensive system was actually installed BEFORE the price of metal went nuts
and it was over $10,000.
Flex duct requires someone that isnt a hack to install it correctly. While
its simple, and quick, it needs to be supported correctly, thought out in
advance if there is a long run, and the proper manual D is not an option,
period. It MUST be done correctly.
Flex duct offers the advantage of no code requirements on a particular run
length, when sized right, and the insulation and duct are all in one nice
neat package. Boot attachments are quick and easy, and require in some areas
nothing but some duct mastic, and two tie straps and the proper tension
Prices vary. I use a very high quality duct, and have to as flex is the
option more people chose when they see the prices of metal. Again, it will
depend on number of runs, how hard it is to replace the existing, and the
sizes needed to do it right, but expect quotes over $1000 normally for any
sort of quality work and if you have more than 7 runs to be replaced. The
crap sold at Home Depot and Lowes is that....total and complete crap. You
cant use those prices, to get ballparks, since most of the stuff a pro will
use costs more than twice that wholesale.
Pricing will be by the amount of materials used for sure. Some will flat
rate the job, and others will do it by time and materials.
I flat rate on this type of thing, since I have run into some issues that
are unforeseen and if the customer had paid time on the job, it would have
ran WAY more than I quoted.
My guys as a time example can normally remove and replace a complete system
on what you might call an average home in under a day, if its flex, and I
have been known to personally do a remodel by myself, as in solo, no help,
in one day...including the furnace and AC installation.
This was in a home with NO ducts at all...just a Monitor heater. I have
another coming up in the next couple of weeks and I might take a little
longer, but I plan on taking pics for the website, so it might take a day
and a half.
Its not a pretty home, but one of my remodel contractors that I work with
bought it, and wants central air and to remove the Monitor that is in there
and get away from oil so that whoever buys it has cheap heat.
I would dare to guess that you dont have insulation on the inside of the
duct if its wrapped.
If its metal on teh outside, it MIGHT be, but thats rare.
only takes a second and when in doubt..
Washington DC? Washington state?
Neither...closer to DC but we are not licenced up there.
Just in NC and SC.
That was a detailed reply!
I have some update on my issue. When u say sealed I am assuming that all
the registers being in place too. Is that right ?
I got a shopvac and tried to remove some of the grains/seeds etc., that
had fallen down there and guess what I got- a coke can and tons of other
junk and all this with cleaning only two registers! rat droppings too. :
I put my hand in one of the registers and after the metal end thingie
(floor box ?) came across plastic sheeting like material inside the
duct. It seemed to be connected to the duct with seams of somesore, and
a little frayed at the point where the floor box connected to the duct.
Looks like right now I'm looking at having to replace the ducts at some
point of time soon. Can anyone give me a ballpark figure for how much
this endeavour might cost ? I mean an order of magnitude, for a 2400
Do the HVAC guys charge by the square foot/ time and materials or the
whole job -in one go ? How long do these things take ? I know I have to
ask a contractor but I'd like to have SOME idea so as to not get too
My inspector told me we have metal ducts so I am hoping we can reuse
some of that...dont know if its a square duct. I see only the ends of it
in the furnace room. Have to look in the crawl space for the rest.
I am going to get someone to try some of what you suggested with the
cutting and the mastic. Dont have the stomach to be making holes in
parts of my house.
Any chance u are in the washington area?!
Aargh! I left the shop-vac lying around and it looks like my hubby came
home- saw new toy and tried to clean the registers. I see evidence of
this activity by a small piece of insulation lying off the side of the
The rest of the insulation, I presume has safely been disposed off to
conceal evidence. :)
Here I was worrying about insulation that might be blowing fibres into
the air, now I have NO doubt. I'm a little scared to see what the damage
is like. Hubbies! you gotta love them!
Any suggestions for an air purifier to remove the fibres ? till we get
some $ to get the heating ducts replaced ?
Steve, pity you are in NC/SC, I am in Washington State- near Seattle.
Do you have any suggestions for a good- reliable HVAC guy who actually
would bother to explain to me, what he is doing ?
I am sick of all kinds of service people just not telling me what they
propose to do... I have to try VERY hard to get any information out of
them. I guess it woud be somewhat understandable if they thought I was a
DIY who'd attempt this myself after sneakily extracting all sorts of
info from them. One look at me and they'd know. DIY- NOT.
I am truly interested in learning about my home. sigh.
Your post have been extremely useful in understanding some of this
stuff, do u have any links where they have some basic description about
duct replacement and heating system replacement.
BTW- our furnace - 80% efficiency replaced in 2001. So its too new to
throw out and too inefficient to live with- such is life.
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.