Category Archives: Building Science

Building Science Part 3: Moisture Flow

Controlling moisture flow in a building has significant impacts on occupant health and safety, comfort, building durability and energy efficiency. This section will cover the basics of moisture and its effects on the house system. It will also discuss how geographic location and house type can affect choices of moisture control strategies.

Applied building science is concerned with four different moisture transport mechanisms and the effects of that moisture flow:

  • Bulk water movement (rain, snow, or groundwater)
  • Capillary action (capillarity)
  • Air transported moisture



Building Science Part 5: Conclusion

Over the past few months, we’ve discussed some of the main factors in creating a comfortable and safe home. The end of most of these articles contained a note about reducing risk and increasing tolerance. Let’s talk about how these ideas fit together. In the last 50 years, home building has changed dramatically – increased insulation, tighter homes, smaller chimneys, more efficient HVAC, reduction of good flashing details, cementitious siding, power attic ventilators, to name a few. All of these things are designed to create more comfortable homes. If you simply throw one idea in without regard to how they fit together, you’re increasing your risk. 

Risk is inherent in building a house. The homeowner may not like the wall color that you had agreed upon. The plumber may forget to run a pipe and no one notices until after the wall has been sheet-rocked. The weather may put your schedule 3 costly weeks behind. And then there’s the more long-term risks, like mold, houses that won’t heat or cool properly, polluted indoor air and lawsuits. Why make building riskier than it already is? The Environments for Living program, from where most of this information has come, lists 7 steps to risk reduction:

  1. Airtight
  2. Provided with fresh air (mechanical ventilation)
  3. Insulated right
  4. Equipped with properly sized and installed HVAC
  5. Pressure balanced
  6. Moisture managed
  7. Combustion safe

Every home is an interactive system that needs to have all of the above in place to function properly. One thing out of whack can contribute to failure of the entire system ou acheter viagra generique. When building for durability, energy efficiency and health and comfort of occupants, it is important to remember that the comfort of a house is in the building envelope. If you start with this in mind, you have the the basis for a low risk, high tolerance and, most importantly, happy customer.

Building Science Part 4: Indoor Air Quality

Indoor Air Quality 









Anyone can smell the air and tell if there are indoor air quality problems. However, many air problems may not stink now but will cause one later.

There are five types of pollutants in houses:

1. Volatile Organic Compounds (VOCs) – cleaning products, aerosols, pest killers, furniture finishes, fabricsand building materials

2. Particulates – pet dander, dust mites, mold spores,
dust, smoke and pollen

3. Soil Gases – Insecticides, liquid fertilizers, septic gases and, of course, radon

4. Moisture-Borne Pollutants – Moisture in the air is a vehicle for dust mites, mold, etc., although the moisture itself is NOT a pollutant

5. Carbon Monoxide (CO) – Comes from gas appliances, fireplaces, wood stoves, unvented kerosene heater, cars parked in attached garages, and from outside air So sources both outside and inside the home can affect our quality of air. So how do we control these things?

  • Eliminate pollutants from the home. A great idea in theory, but in reality, the next 2 steps are more likely.
  • Reduce the amount of pollutants.
  • Separating pollutants from the living space. Detached garages, for instance.
  • Filtration. Your furnace filter is a great place to start but testing shows that standard fiberglass filters remove.
  • less than 20% of all particulates.
  • Ventilation. There are 2 kinds of ventilation. Passive ventilation occurs in leaky houses and when the windows are open. Therefore, in today’s tight houses, we need active ventilation, such as kitchen exhausts (@100 CFM intermittent), bathroom exhausts (@ 50 CFM intermittent or 20 CFM continuous) and heat-recovery ventilators (HRVs) or energy-recovery ventilators(ERVs). A minimum rate of 7.5 CFM per person plus .01 CFM per square foot of conditioned floor area is needed to bring in sufficient fresh air.
  • Controlling pressure.

Building Science, Part 2: Heat Flow

Last month we discussed air flow and its causes. This month, we delve into heat flow. First, let’s cover the basics. Conduction, convection, and radiation are the three mechanisms by which heat moves. Conduction occurs between objects that touch each other, such as when your warm hand touches a cold window during winter. Convection is the movement of hot air upwards and cold air downwards. Radiation is the movement of heat across open space. So, how do we affect heat flow in a home? There are four main steps to avoid thermal related issues.

  1. Framing must protect insulation
  2. Insulation must be installed correctly
  3. Enhanced air sealing
  4. High-performance windows (installed correctly)

An important note here is that the comfort of a house is in the building envelope. While activity, clothing, relative humidity, air velocity, temperature and radiant surface temperatures all affect comfort, the building envelope will dictate how much these factors alter the comfort of the occupants. An inadequate envelope will result in a home that never functions quite right peut on se procurer du viagra. The first step to controlling heat flow is to reduce convection. An effective air barrier that separates the inside, conditioned air from the outside air begins with framing. It is extremely beneficial to explicitly label the air barrier on the house plans. Enhanced air sealing, when coupled with air barrier framing, is the second part of reducing convection. Good air sealing requires significant attention to detail. Insulation problems generally include gaps, voids, compression or insulation/air barrier misalignment, all of which add to conduction. While the insulator can be at fault for these issues, often they are merely ‘playing the hand they’ve been dealt’ by the subcontractors before them. Certain insulation systems, such as the Blow-in- Blanket System, can reduce the occurrence of these problems. Helping you reduce risk and increase tolerance in any given home is the driving force behind building science and part of our mission. Next month – Moisture Flow.

Building Science, Part 1: Air Flow

This article is the first in a series on the Principles of Building Science – Air Flow 

If Uncontrolled Air is the enemy to comfortable, efficient and healthy homes, what causes air to flow in and around a home? First, some basic facts about air: air always moves from high-pressure areas to low-pressure areas. One of the main tenets of high school chemistry is that nature will always seek to create equilibrium. Hot air rises and cool air falls. If one cubic foot of air leaves a building, one cubic foot must enter the building.

Do you know where the replacement air flow is coming from in your house?

The next fact is that air will always seek the path of least resistance. And air will carry things like pollutants and moisture with it. With this introduction behind us, let us get to the forces behind air pressure. The first is wind; a subject that we are familiar with here in Kansas. Wind can create positive pressure build up on the side of a building that is being blown against while creating a negative pressure area on the opposite side. Then, the building will take in air on the positive side, while losing air on the negative side. The amount of holes and effectiveness of air sealing measures will dictate how much air is moved where. The second force to discuss is heat, which moves air by a process called Stack Pressure inside buildings. Temperature differences between the outside and the inside of a building create pressure on the building. In cold weather, for instance, the hot air on the inside will try to force its way up and out through the roof – an effect that is magnified by additional stories in the structure. Fans, the third force, can create pressure differences inside a home as well. Leaky building envelopes, ducts or an imbalance between supply and return ducts can dramatically alter the building’s performance and the comfort and health of the occupants. So, why dedicate advertising space to discussing basics of building and building science? Helping you reduce risk and increase tolerance in any given home is part of our mission. And this brief introduction only scratches the surface of building science. Next month – Heat Flow.