Construction Archives - Dawn Killough, Freelance Construction Writer

What Affects R-Value of a Building?

The insulation value, or R-value, of a building is a sum of the components that make up the outer shell. This often includes siding, insulation, framing, and drywall. There are certain parts of a building, however, that detract from its ability to insulate.

*R-value affects heat loss in a building*

Doors and Windows

As much as we love, and need, doors and windows, they are not good for a building’s insulation value. Doors open and close, allowing air to move freely inside and out. Additionally, it can be tough to completely seal the gap around a door, causing even more air leakage even when the door is closed.

Windows are also not very insulating. Recent changes in glass technology and the use of multiple panes of glass have improved their insulating properties a bit, but they still can’t compare with other materials.

Just to further confuse the issue, windows have to have their own label to measure their insulating value – the U-factor. U-factor is the inverse of R-value, so the lower the number, the better insulation the window provides.

One of the characteristics that affects the insulating ability of a window is SHGC (solar heat gain coefficient), a measurement of the amount of heat caused by sunlight that is allowed through the glass. The lower the SHGC, the less solar heat the window transmits. It is important to note that both of these measurements, U-factor and solar heat gain coefficient, only apply to the glass in the window, not the frame.

How can you increase the insulation value of a window? Options include: insulating window shades, window tinting or film to prevent solar heat gain, and the use of multiple panes of glass with insulating gases (such as argon) inserted between the panes.

*Doors create opportunities for air to flow in and out, reducing energy efficiency*

Air Gaps

Air gaps are the bane of insulation! As much as insulation and other building materials try to keep the outside out and the inside in, gaps between materials, or holes within materials, defeat their purpose.

The fix is easy – no air gaps! Completely sealing the space where materials meet with caulking and making sure that no holes are allowed will help decrease air gaps substantially. They can’t be eliminated completely, but the less there are, the better.

Bridging

Bridging, or more formally thermal bridging, can best be described by the phrase “taking the path of least resistance.” Air temperature will travel through the areas of a roof or wall with the least R-value, providing a “bridge” for the hot or cool air to reach the inside of the building. This may seem a bit confusing. An example from Green Building Advisor will help:

“Suppose your walls have 6″ fiberglass batts… Every 16 inches on center in that wall is a 2×6 or 2×4 stud. The fiberglass has an R-value of around 3.5 per inch, and the stud is around R-1.2 per inch. The wood studs allow heat to flow through the wall assembly at a rate that is 3 times faster than the heat flow through the surrounding insulation. While the advertised R-value for a 6-inch fiberglass batt is R-19, the building assembly’s effective R-value is about R-3 lower.”

What a bummer! How do we fix this? A few options are available: use advanced framing techniques to limit the number of studs, install insulation between the studs and the inside or outside surface to break the bridge, or use alternative building materials that do not require the use of studs, such as straw bale or SIPS (structural insulated panels).

Putting It Together

R-value isn’t the only characteristic to consider when choosing building materials, but it can play an important role in improving the energy efficiency of a building. Wall and roof assemblies should be evaluated at their weakest point, and steps taken to combat the infiltration of air or temperature whenever possible. Purchasing efficient windows and doors will also help improve efficiency.

Photos courtesy of Depositphotos.

What Is R-Value and Why Is It Important?

R-value is a measurement of how much a building material protects one side from the heat or cold on the other side. A higher R-value means that a material insulates better than one with a lower value.

*R-Value affects the amount of heat lost through walls, doors, and windows*

What Is R-Value?

In order to get an idea of what these values are, here are a few examples of common building materials and their R-values:

1/2″ drywall – 0.45
1/2″ plywood – 0.62
4″ wide brick – 0.80
1″ of concrete – 0.52
Single pane of glass – 0.91
2″ insulated metal door – 2.00

R-Value of Building Insulation

Building insulation has different R-values depending on the type of material being used and the thickness of the material. Insulation made from different materials is used in different areas of a building, and is designed to be used in many types of construction.

*Roll of fiberglass insulation material*

Here are a few common types of building insulation:

Fiberglass – This is the most common material used in residential construction, and it is made up of blown glass threads that are either matted together into batts or distributed loosely. The fiberglass batts are either stuffed into the spaces between the studs in the exterior walls of a building, or they may be laid down on the bottom of an attic space. Other forms of fiberglass insulation, such as loose fill or boards, are used in other locations, such as a basement or crawl space. Fiberglass insulation comes in a wide range of R-values, most commonly from R-11 to R-38.

Foam – Spray foam insulation is made by mixing two chemicals (isocyanate and polyol resin, if you are interested) that react to create foam that expands to fill the space it is placed in. It can be shot into spaces through small access holes, making installation in retrofit projects easier than standard batts. There are two types of spray foam – open and closed cell – with closed cell being the most dense and therefore having a higher R-value. Foam averages R-5 to R-6 per inch, compared to R-2 to R-4 per inch of fiberglass.

Recycled denim – Blue jeans and other denim products are shredded and the cotton fibers are woven together to form batts, similar to standard fiberglass insulation. The denim used to produce this insulation is post-consumer, so it removes products from the waste stream and repurposes them. Denim batts provide slightly better R-values than similar thicknesses of fiberglass.

What Does It Mean?

So, why is all this important? R-value is an additive property, meaning that by layering several materials on top of one another, the insulating value of the assembly will be the sum of the individual products. For example, a wall made up of a sheet of drywall, R-11 insulation, and a sheet of plywood would have a total R-value of 12.07 (0.45 + 11.00 + 0.62). Think of it as adding multiple blankets of varying thicknesses and materials to keep warm.

There are a few more things to consider when determining how insulating a structure is, but for the most part, the higher R-value the building shell has, the easier it is to heat and cool and less energy is needed to keep it that way. Of course, there are things like doors and windows that don’t insulate as well or let in outside air, lowering the insulating ability of the building.

When designing a new structure or remodel project, it is important to try to increase the R-value of as much of the exterior walls, roof, and floor as possible. A well-insulated building is more energy efficient and less expensive to heat and cool.

Photos courtesy of Depositphotos.

Construction Contract Clauses to Watch Out For

Construction contracts can be complicated documents and should be reviewed by legal counsel before signing. They are filled with clauses that attempt to protect the party creating the document. There are some specific clauses that contractors and subcontractors should pay attention to before signing, as they can lead to disputes down the road.

Construction contracts can be complicated documents and should be reviewed by legal counsel before signing. They are filled with clauses that attempt to protect the party creating the document. There are some specific construction contract clauses that contractors and subcontractors should pay attention to before signing, as they can lead to disputes down the road.

Scope and Price Definition

One of the primary purposes of writing a contract is to define the work to be done and set the price for that work. It is important to review the scope of work and price as listed in the contract. Often the contract will provide for a broader interpretation of the work involved, such as requiring work that may be implied or inferred from the drawings and/or specifications.

Also check the pricing, making sure that items such as taxes, bonds, insurance, permits, and other fees are included or not included as per the proposal. It is important to note that just attaching the proposal to the contract document does not incorporate it into the contract. It must be explicitly mentioned in the contract language to be considered as part of the terms of the agreement.

Owner Contract Clauses

Often the contract with a subcontractor will include a reference to the owner contract, tying the subcontractor to the terms of that agreement. Language like this is included in the AIA’s subcontractor/contractor contract, Form A401. Subcontractors should request to review the owner contract with the general contractor before signing such contracts. Clauses that can be subject to this flow-down language include termination clauses, claims procedures, indemnification clauses, and dispute resolution clauses. Subcontractors should be aware of the terms they are agreeing to.

Payment Clauses

Payment clauses should always be reviewed carefully so contractors are familiar with the requirements for payment. Pay-when-paid and pay-if-paid clauses can cause issues. Pay-when-paid clauses state that a subcontractor’s invoice becomes due when the general contractor receives payment from the owner. Pay-if-paid clauses state that subcontractors will be paid only if the owner pays the general contractor. This passes the risk for owner non-payment to the subcontractor. Either way, subcontractors need to review payment terms and know when payment will be made.

Delay Clauses

In reviewing delay clauses, watch for language that doesn’t allow for recovery of costs related to project delays. Most contracts will allow for a schedule extension, but not necessarily recovery of costs. Check state laws to see about the enforceability of these clauses in your state. Federal contracts allow for recovery of costs if the delay was caused by the federal agency.

Summing Up

Construction contracts are complicated, and it is important that the parties read them before signing to make sure there are no hidden risks. The construction contract clauses mentioned above can lead to issues down the road, so getting clarity on what they mean and how they apply to your company is critical. Always seek legal counsel, before signing, if you have any concerns.

Source: Supplementary Conditions

Photo: DepositPhotos

Is It Illegal to Not Have a Safety Committee?

In at least 16 states in the U.S., the answer could be yes. These states have various requirements, based on the number of employees and a company’s loss record, that may make it illegal for a company not to have a safety committee.

Alabama
California
Connecticut
Maine
Minnesota
Montana
Nebraska
Nevada
New Hampshire
North Carolina
Oregon
Rhode Island
Tennessee
Vermont
Washington

*Please check with your state to verify requirements, as laws may change.

How to Start a Safety Committee

With this information in mind, employers need to know how to set up and run a safety committee. Here’s how in four easy steps:

Select or elect committee members. There should be representatives from all departments, divisions, and supervision levels. Company management, or someone with the authority to authorize expenses and decisions for management, should also be represented. Members can be volunteers or selected by workers. Membership in the committee should be on a regular rotation, with workers rotating on and off on a schedule. A chairperson should be elected, and someone should take minutes and they should be typed up for permanent records.
Schedule and hold an initial meeting. At this meeting the committee will determine when and how often they will meet (usually not less than once a month), discussing and prioritizing the duties of the committee, and determining if any subcommittees need to be started.
Responsibilities of the committee may include developing the company’s written safety plan, providing training for committee members and other workers, inspections, incident reviews or investigations, assessing the effectiveness of the safety program and the committee, engaging specialists or speakers, approving safety purchasers, and developing procedures.
Continue to hold regular meetings and make minutes available to all employees. Keep a file or notebook with meeting minutes, inspection checklists, investigations, etc. This information may be required and asked for if there is an incident or investigation.

The goal of a safety committee is to help keep all employees at a company safe and healthy while at work. It is a chance for management to show employees that safety is a priority. While it may be a legal requirement in some states, it is a good business practice for all companies.

Photo: DepositPhotos