Attic Ventilation


Attic Ventilation 

The International Residential Code specifies a 1 to 150 ratio of total net free ventilating area to area of space to be ventilated when it comes to ventilating attics. So, what exactly does this mean and why is it important to ventilate attics in the first place? We’ll start with the second part of the question. Ventilation provides the conditions that allow air to move, obviously. Efficient ventilation systems provide a steady, high volume of air movement. At this point, we should note that simply cutting a 6” hole somewhere in the attic is not creating an efficient ventilation system. The air movement we are discussing needs to be controlled and balanced. The amount of air coming in must be equal to the amount going out, otherwise, the attic will start sucking air from the house or stagnate due to insufficient free vents.

The purpose of ventilation is twofold:

1. During warmer months, it keeps attic air moving and, by extension, make the house easier to cool. Basic physics tells us that hot air rises and cold air falls. By circulating the air in the attic, all the really hot air that would build up in there is pushed up and out. Also, We should note that during really hot months, an unventilated attic seldom loses enough heat overnight to compensate for heat gained during the day.

2. During cooler months, it reduces moisture to keep attics dry & helps prevent ice dams. The warm inside air can hold more moisture than the cool air outside (and in the attic) and as this warm, moist air hits the cold, dry air, it can condense. So, now we’re at the stage to get some practical information. Let’s take a house with an attic with 2000 square feet. Now we’ll divide this by 150 to find the total net free ventilating area, 13.3 square feet. To make sure that the system is balanced, we then divide this number in half because half the vents will be lower and half will be higher. This means that 6.6 square feet (or 950 square inches) of ventilation is required at both the bottom and top of the attic.


Insulating Pipes and Wires


Insulating Pipes and Wires: Right vs Wrong 

What comprises a good insulation job? What should it look like? Where are the most common errors? We’ll take the next few months to look at some common installation issues.

Insulating Pipes & Wires

Let’s start with a sample job: Most of the insulation near the electric box is pressed to the side of it, with little or none behind the box. As a result, there is part of this cavity with no insulation and another with compressed insulation.

Here’s another installation scenario: The installer has taken the time to cut the batt and adequately insulate behind the box. By insulating this way, compression of the batt beside the box is also avoided. Of course, the Blow-in-Blanket System fills voids and gaps around pipes and wires completely. BIBS also increases the wall insulation R-value to R15 in 2×4 walls. However, a good batt installation is possible – it just requires attention to the details.

Insulating Pipes Insulation Wire Insulation Wichita Northstar Pipes Wires

The Easy Way to get R-15 Sidewalls

This month’s installment of the Building Science overview – Indoor Air Quality

In the June issue of the WABA Digest, two separate columns discussed some of the proposed changes to the International Energy Conservation Code (IECC), particularly in reference to wall insulation. As a reminder, the proposed changes are from R-13 to R-15 in 2×4 walls and from R-19 to R-21 in 2×6 walls. I have no intention of debating the merits of this change. Instead, I would like to point out that the easiest way to achieve higher R-values without switching to high-density batts or adding exterior sheathing: Certainteed’s Optima insulation, designed for use in the Blow-in-Blanket System, achieves an R-15 in 2×4 framing and an R-23 in 2×6 construction. The advantages of using Optima are numerous – no gaps or voids, no settling, plus it goes in the wall cavity completely dry. It also contains no chemicals that create noxious odors nor is it a source of food for insects or animals. One of the main concerns about raising the wall insulation R-values is about adding cost and using Optima does cost more than normal batt installations. But given estimates of changing to high-density batts or from 2×4 framing to 2×6 adding around $1,000 to the cost of an average new home, upgrading to the BIBS system with Optima adds less than half that. Plus, you still get all the benefits of having a better insulation job than just thicker batts can give you. Regardless of energy codes now or in the future, Optima may be a better choice to keep your customers’ homes more comfortable.

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.

Window Films and Window Warranties

Most of the time, installing window film will void the window manufacturer’s warranty but the film manufacturers have backup warranties. That is the simplest explanation of the relationship between window films and window warranties but it is also a completely unsatisfactory explanation of a subject that deserves at least a little more thought. For the purposes of this article, we will limit ourselves to talking about double pane glass: low-E or standard, tinted or clear. Single pane glass rarely has warranty issues while triple pane is rare. We will also assume a standard window film from a reputable manufacturer, such as 3M or Vista. Professional window film installations come with 3 warranties.

  1. The easiest warranty to explain covers the film itself. Generally, there is a lifetime warranty covering any kind of deterioration of the film. Deterioration can take the form of bubbling, peeling, hazing; all are symptoms of adhesive failure. Fixing adhesive failure requires removing the bad film and reapplying new film.
  2. The second warranty covers what the film manufacturers refer to as “Thermal Shock Breakage”. Essentially, this means that the film is warranted not to break the glass for a given period of time, generally 2-5 years. The reason why the glass may break is because filmed glass absorbs more heat than unfilmed glass. The added heat stress, on rare occasions, causes the interior pane to crack. Most films designed for home usage are safe on windows, every so often this occurs, generally because of a flaw in the glass.
  3. The third warranty covers seal failure of the glass. The film manufacturers are aware that many glass manufacturers void their warranties, so every film installation comes with a warranty against the seal failing, which is the main reason why the window warranty comes up in the first place. The standard seal failure warranty lasts for 2-3 years. Even better, Vista and 3M offer warranties that will take over the manufacturer’s warranty at a minimal cost. That way, no coverage is actually lost.

Selling with Energy Efficient Mortgages

There are many ways of approaching Energy Efficient Mortgages (or EEMs) but simply being aware of them can be worth the extra attention – and qualify more buyers. Potential buyers can qualify for larger houses through energy efficient building. An FHA-approved lender can expand the borrower’s debt-to-income ratio by 2% because financial institutions that offer EEMs know that less money will be spent on energy costs, so more money can be spent on the house itself. With natural gas prices continuing to rise, this could be a very important selling point. Plus, more first-time buyers can qualify using EEMs. In fact, the EPA estimates that an average of 6.8% more families would be able to get a loan when using more efficient guidelines. As interest rates look to be inching upwards, having a pool of qualified customers can offset higher rates. Fannie Mae and Freddie Mac, not to mention HUD and the VA all offer different programs regarding energy efficiency. In fact, one of the mortgages even offers 100% financing on the value of the home. Using EEMs is not necessarily a more complicated step. As Fannie Mae CEO Franklin Raines pointed out in a recent interview, “Qualification is much quicker and easier. Lenders can use their automated loan underwriting systems to get an immediate decision.” While we are not in the business of making loans, we do have information and services that can help in the design or build stage. A more efficient home is not necessarily a more expensive one. Let us know what you need and we can point the way. The Comfort Corner Information for this article was found at theAlliance to Save Energy website and at the U.S. Department of Energy Efficiency and Renewable Energy.

Foam vs Fiberglass vs Cellulose

When it comes to insulating a new house, there are a few ways to get it done. The main three ways of insulating a new, wood or steel framed house are fiberglass, cellulose, and spray foam. So, other than the obvious, how do these products differ? Is one superior to the others? What really counts when it comes to insulation? For the next couple of months, we’ll be taking a look at these different systems to try and sort them out. To help objectivity, we will use NAHB’s study, Field Demonstration of Alternative Wall Insulation Products. We start at the beginning – with definitions: Fiberglass batts – Made of fiberglass, batts come in wide variety of sizes, thicknesses & R-values. They are available with a kraft facing, which is generally inset stapled to the cavity wall, or unfaced, also called friction fit, which is covered with a separate vapor barrier. The

They are available with a kraft facing, which is generally inset stapled to the cavity wall, or unfaced, also called friction fit, which is covered with a separate vapor barrier. The Blow-in-Blanket System – also made of fiberglass, BIBS is a loose-fill product that is blown behind a net that has been stapled to the studs. Holes are punched through the net when and where the installer blows the material into the cavity. R-values depend upon the cavity depth and density blown but can be up to 4.2 per inch Spray Cellulose – Made from recycled newsprint, cellulose is applied to wall cavities by a hose that mixes the material with water to activate a binder that has been mixed in. Loose material from the installation is often recycled back process.

Low-Density Polyurethane – Foam, made by combining polymeric isocyanate (MDI) with a propriety resin. Soy-based foams are also available. R-values are about 3.6 per inch and the foam is open-cell. Higher density, closed-cell foams are also available at a premium. If we stopped here, we would be forgetting one of the more important aspects of a good insulation job – the air sealing or polycel/caulking. In fact, this is one of the most important parts of an insulation job – as we will see later. For now, we need to note that there are different levels of air sealing and they vary widely. A standard air seal usually involves caulking attic penetrations & clinking windows with fiberglass, while and upgraded air seal involves sealing windows with foam or caulk.