Archive for September 2014
Vapor Retarders VS Air Barriers
Water vapor moves from the warm
side of a building to the cold side. We must design our insulation
system to
allow trapped water vapor to get out and keep exterior water vapor from getting
in.
Materials that retard the flow of water vapor
are called impermeable. Materials which allow water vapor to pass are called
permeable. Naturally there are degrees of permeability and all materials and
systems have varying degrees of permeability. Most building codes require a
vapor retarder whose permeability is 1.0 or less.
Vapor barriers and
air barriers are two different things. The purpose of air barriers is to have a
structure whose holes, tears, openings, and penetration are closed up or as
much as or possible because with differences in air pressure, air can move
easily through these “openings” and carry moisture through these openings. An
air barrier is not a vapor retarder.
In practicality it
is impossible to eliminate all penetrations, so it becomes a matter of
controlling as much as common sense will allow. So, HVAC systems can be designed
in concert with your air and vapor barriers to control ventilation,
dehumidification, and air pressure. Your local climate and four seasons affect
this as well.
Welcome to Areva
Shireman Construction and the Chamber of Commerce of Harrison County welcomes Areva Pharmaceuticals in this issue of 'This Is harrison County'.
Thoughts on Insulation
Insulation
performs many functions, but if we were to boil it down to two things:
1. Keep
the heat away during the summer
2. Hold
our heat in during the winter
Ridged insulation
and some spray foam can be air barriers if properly installed but, generally,
fiberglass, rock, wool, blown in cellulose etc is not an air barrier.
As we said before,
the key is to energy efficient buildings and environmentally friendly buildings
is the proper use of insulation. The amount of energy used to produce any
kind of insulation is over ridden by the energy saved during the life of the
building.
When using
fiberglass, do the best you can to make it “full fit” the cavity. Damp spray
cellulose will dry toward the interior so the interior will have to be designed
to allow that interior drying. Cellulose is not a vapor retarder.
Spray foams have
come a long way over the years. Many of them have excellent air sealing
capabilities. These foams can quite often reach the hard to reach areas and
give you a better insulation barrier. Think about building movement and the
tolerances required. Low density foams “move” better than high density foams.
Nurturing Innovation Hubs
Much is being written about innovation and entrepreneurship. Here's another interesting article confirming that.
- Mark
- Mark
Shireman 4th Generation Additions!
 |
| Natalie (left) and Luke (right) cuddling up. |
Shireman Construction is pleased to announce new additions to our potential fourth generation of builders (plant the seed early)!
Jeff and Veronica Shireman's twins Luke and Natalie were born on August 22nd. Luke weighed 6 pounds 15 oz. and Natalie was 6 pounds 7 oz.
They recently had a few photos taken with big sister Abby (22 months).
Jeff is slowly transitioning back to the office while Veronica and he remain sleep deprived. The babies sleep 20 hours a day but only 3 hours in a row!
Thanks to everyone who sent best wishes.
 |
| Big sister Abby with the Twins. |
Drywall (Sheetrock) and Paint Basics
Drywall is gypsum board. We want it
to look nice, give us some fire protection, reduce air flow, etc.
Sheetrock,
itself, can expand and contract fairly nicely. When it’s cracking it’s because
the substrate supporting it is moving. We know that all building materials
move, so our goal is to build in expansion joints to allow the substrates to
move.
Property
installed and taped drywall makes a good air barrier. When you add your paint
you have a nice vapor retarder. This is why architects like the versatility of
drywall. Also, you’ll notice fire code drywall being used as draftstops, smoke
walls, and firewalls.
Treated
gypsum board is frequently specified to be used in wet areas. If the budget
will allow it, substitute their “green board” for cement board. Cement board
will last longer.
Although
not specified all over, we like to use 5/8” fire code drywall all over. The
5/8” F.C. is not extremely more expensive and when applied properly over each side
of a wall you’ll get a one hour fire rated system all over.
Stain
breaks down in ultraviolet light more quickly than paints. This is why you have
to “re-stain” so often. Quite often “solid body” stain is really a thin paint,
so its value is limited.
Primers
are used to provide a surface to keep the finished paint from over absorbing
and provide a more adhesive surface for the paint. Primers also attempt to
reduce the effect of tannic acid and salts from wood. Normally, oil based
primers hold back tannic acid in wood. Latex primers seem to work okay on
masonry, drywall and concrete. Generally, redwood and cedar should be primed
with an oil base primer.
Foundation Basics: Water Management
When it comes to controlling water at the foundation level, your goals are:
1. Keep
the groundwater out
2. Support
the building above
3. Support
your HVAC design
Water moves
through foundations many ways, via water vapor, hydrostatic pressure, etc. Your
first priority is to design systems to keep the water moving away from your
foundation in the first place, the management of water. No structural system by
itself is water tight.
If utilizing a
basement:
a. Perforated
drain tile surrounded by coarse gravel
b. Coarse
gravel under the slab and polyethylene type vapor barrier
c. Damproofing
on the exterior side
d. Roof
precipitation flowing away from the foundation wall
If utilizing a
“slab on grade design”:
a. Roof
water is directed away from the foundation
b. Vapor
barrier on the bottom of the slab
c. Drainage
gravel under the slab
Coating an
exterior foundation with bituminous materials creating damproofing. Damproofing
resists the capillary forces of water, but not the hydrostatic forces.
“Waterproofing” resists the hydrostatic pressure forces of water. Keep water
flowing away from your building and foundation and therefore create no a
hydrostatic environment.
Fire Preparedness
This article reminds me of when I was in school. It's an interesting perspective on a big picture issue.
-Mark
-Mark
'Critter' Management
Keeping your
building resistant to dust and critters is one of your highest priorities:
1. Seal
up your exteriors and inspect them annually. Check your walls, roofs, and
foundations for holes and penetrations.
2. Seal
up your interior baseboards to keep critters from moving around should they get
into your building.
3. Your
building should make it difficult for critters to find food and water. Keep
water out, keep your plumbing and ductwork from leaking. Keep the food in
sealed containers. Keep your waste in sealed containers. Keep wood and paper
from getting wet.
These steps can
reduce your expenses associated with pesticides and critter removal vendors.
If budgets would
allow, use HVAC filters with MERV ratings of 6 to 8. ASHRE 35% or better.
