you should hire an energy rater.
blower door test the house, test the ductwork prior to any
work being done. (once work is completed re-test..and if you
chose..intermediate inspections/testing)
this way you know where you are now and what your target is
going into the project.
verification of work is to assure you that what you paid for was
actually achieved.
once you know how tight the house is..and how much duct leakage
you have,a target for sealing will be provided.
your rater will be able to show you leakage areas & give you
guidence as to how to seal these areas.
depending on where the leakage is, you'll address in order of
importance. attic to living space leaks first.
these will include any recessed lights that aren't air tight,
oversized cuts at stove vents, bath fans, supply boxes & return
air.
openings into the attic allow attic temps along with insulation
particles & voc's into the house..the air barrier between attic &
living space needs to be as perfect as possible.
any thermal bypasses..fireplace boxing open to attic, openings from
attic into living space will also need to be sealed..then insulated.
ducts mastic sealed, not foil or duct tape, but mastic & mastic tape only.
no great suff foam for duct or returns. none, mastic only. make that a requirement.
once ducts and returns are sealed..install a 4" media filter.
condensation on windows is probably from high relative humidity.
in my/your/our hot humid climate target RH% is 50%. realistically 30% isn't going
to be easy to achieve..or even worthwhile. once house/ducts are sealed then
less outdoor high RH air will be entering. 50% RH will be comfortable & tstat
settings will be higher as air will be colder & drier.
then to add a whole house dehumidifier would be the next step.
I have an april aire dehumidifier. these units can be set up to
add fresh air to the house. Teddy Bear is the guy you'd want to talk
with here about these units. his help was invaluable in helping me
to determine the best set up for my unit.
I think you'll find that you'll need less than 220 cfm of fresh air, but
ashrae 62.2 ventiation strategy will determine that amount. to get these
numbers you'll need the blower door test to determine air changes per hour
that your house has. there is a bit more to it that adding air!
start with an energy rater that has existing home & allergy experience.
you need to know where your house is...where you want to improve it..
and what those improvements achieve. then you determine the method
of dehumidification, fresh air & better iaq.
and have them verify the installs, and the performance of the installs.
I see lots of people spend a lot of money on uv lights, crazy expensive filtration
systems & never solve anything.
without considering the whole of the house
instead of different parts of it..you won't get the solutions you desire.
check with resnet for an accredited experienced energy rater in your area.
they should be able to recommend companies they have worked sucessfully
with on other projects.
you'll want an experienced installer for the whole
house dehumidifier & people who understand what air/duct sealing actually
entails.
quite a bit of the work can be diy if you chose. if you plan to hire someone
to do the air sealing..you should have them on site to 'see' the leakage areas
so that they understand what is to be achieved.
you can do a LOT with a couple of cases of caulk & mastic to lower air &
duct leakage.
http://www.resnet.us/energy-rating
at the bottom of the page you can search for a rater in your area.
talk with several & describe your concerns to each. ask how long they
have been in the business & for refrences of people with similar issues
to yours.
find someone you are comfortable with that will take time to
explain & actually show you the air leakage sites, rather than someone
just telling you how much leakage the house/ducts have.
best of luck.
The cure of the part should not be attempted without the cure of the whole. ~Plato