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how much insulation

How Much Insulation Should You Use?

By Tobias Roberts Rise Writer
Jan 22, 2021

Research by the North American Insulation Manufacturers Association (NAIMA) estimates that roughly 90 percent of existing US homes are under-insulated. Improved energy-efficient construction techniques are increasingly available to builders and contractors. But, it is, unfortunately, safe to assume that many new builds continue to be under-insulated. Air leaks around window and door frames and older, single-pane windows can amount to about 25 percent of all heat loss in homes. The remaining 75 percent of unwanted heat loss and heat gains driving up your energy bills are mostly attributed to insufficient insulation in your home's walls, attic, roof, and foundation.

So how much insulation should you ideally use in your new home or renovation? This short article will start by looking at the minimum amount required by local building codes - depending on your house's location and climate. We will then turn our attention to the insulation used by high-performance homes that meet the highest sustainable building standards.

Framed and Insulated Walls

Important Insulation Terminology

Before we look at the exact amount of insulation required for specific climate zones, understanding the basic terminology related to insulation will help us better understand what we are looking at.

What is R-Value?

The R-value of different insulation materials is a rating of an insulation product's effectiveness as determined by its thermal resistance or insulation value. The higher the R-value, the more insulated the home will be. R-value is measured by Imperial units and is the most common rating of insulation used in the United States and even some 'metric' countries like Canada. You can find a helpful chart showing the estimated R-value per inch of a wide range of common insulation materials here.

What is U-Factor?

The U-factor, also known as the U-value, is a rating you'll more often see on windows or doors, and it's essentially the opposite of an R-value. It is a measure of how fast heat will transfer through the product. For U-factor, lower is better. Check out this Rise energy-efficient windows buying guide for a more in-depth analysis of the U-factor for windows.

What is RSI?

RSI is the same concept as R-value but in metric units. To convert an RSI value to an R-value, multiply by 5.678. Again, the higher, the better. You can expect to find RSI units for products made in the United Kingdom, Australia, or New Zealand. Knowing how to convert this measurement can help make sure you are purchasing insulation products that will maximize your home's energy efficiency and thermal performance.

Effective R-Value vs. Nominal R-Value

There is an essential difference between effective R-value and nominal R-values to make things even a bit more confusing.

What is Nominal R-Value

The nominal R-value is the insulation value (R-value) of the insulation layer only. For example, a 6-inch layer of mineral wool insulation batt has a nominal R-value of R-24.

What is Effective R-Value?

The effective R-value is the insulation value of that part of the building when it's fully assembled. 

This measurement considers the R-value of all the different materials that go into the total wall construction, including wood, concrete, drywall, siding, etc.

For walls with framing extending from the exterior to the interior, the effective R-value is lower than the nominal R-value because heat is lost through the uninsulated frame, a process called thermal bridging

Rise insulation diagram
Figure Credit: Dane George

Consider the example above. A 6-inch wood stud wall with mineral wool insulation in the cavities has an effective R-value of R-20 instead of the R-24 of the insulation itself. It is essential to discuss the difference between effective R-value and nominal R-value with the contractor you hire. This way, you will make sure that they minimize thermal bridging during the construction or renovation process.

When talking about a material's insulation value, people usually mean the nominal R-value, but that is not always the case. It makes the most difference when you consider walls with a 'thermal break,' a continuous layer with no thermal bridges. These walls have a higher effective R-value than walls without a thermal break. To optimize your home's energy efficiency, you should also consider all the insulation and other structural components' interactions. This method is known as the whole-house systems design approach. According to the US Department of Energy, "this approach considers the house as an energy system with interdependent parts, each of which affects the performance of the entire system. It also takes the occupants, site, and local climate into consideration."

Rise 2009 IECC Code Summary Table
Data Source: US DOE

How Much Insulation Do I Need at a Minimum?

The local building or energy code is an excellent place to start to know the minimum amount of insulation you need for your walls and attic. In Canada, the National Energy Code of Canada for Buildings 2015 has been adopted by many provinces. However, in the coming months, changes to the National Building Code are expected to be enacted. These changes will help improve Canada's built environment's efficiency, reduce energy use and greenhouse gas emissions, and put Canadians to work in the clean-energy sector. You can follow these expected changes here.

In the United States, many individual states have adopted the 2009 International Energy Conservation Code (IECC). This code puts forth a minimum nominal R-values for walls, roofs, and floors. Keep in mind that your local climate plays an important role. In winter, Canada and the northern US states typically fall in climate zones six or higher, colder places. The west coast and the southern United States are in climate zones five or lower, which have warmer winters and need less insulation. You can find your climate zone on a Canada or the USA map.

Unfortunately, many people believe that the IECC minimum requirements are too low for proper insulation. Local building codes continue to play a significant role in determining the minimum requirements. The Insulation Institute has published a helpful website where you can find up-to-date information on residential building codes and standards by state.

Passive House In Scotland Tom Manley Riba Journal
Passive House In Scotland. Photo Credit: Tom Manley via The Riba Journal

How Much Insulation Does A High-Performance House Need? 

Suppose you are looking to build a high-performance home that maximizes energy savings. In that case, you will need to go beyond the code's minimum standards.

How much beyond? Most high-performance building standards like R-2000 or Passive House don't specify the exact thickness or R-value. Instead, they require you to add enough insulation to keep your home's expected heating and cooling demand below a defined maximum amount. This measurement is best analyzed by an energy assessment professional, using energy modeling software like Natural Resources Canada's HOT2000 program or the Passive House Planning Package.

Here are three examples from different climate zones to illustrate how much insulation is used in super-efficient homes.

Claire Lightfoot passive house
Photo Credit: Claire Lightfoot

How Much Insulation Does a High-Performance House in a Moderate Climate (Zone 5) Need?

This property is Claire Lightfoot's sustainable home on Vancouver Island, British Columbia, Canada. The Island has mild winters because of the Pacific Ocean. This house is built according to the Passive House standard. The table below compares Claire's insulation for her home versus the minimum required for her zone by the British Columbia Energy Code.

Claire's Passive House Insulation

For every part of the home, Claire has insulated to levels more than double the minimum required by code. By doing this, she has a dwelling that practically heats itself and only needed a minimal and low-cost back-up heater.

Naugler Passive House
Photo Credit: Tim Naugler

How Much Insulation Does a High-Performance House in a Cold Climate (Zone 6) Need?

This home is named the Naugler House and is located near Fredericton, New Brunswick, Canada, and is considered the most energy-efficient home in that province. It's in a cold winter climate zone (zone 6) and was built to the Passive House standard. Here's how the insulation stacks up against the energy code for the area.

Naugler Passive House Insulation

Once again, all the home's surfaces are insulated to more than double the minimum R-value required by code. The floor slab is exceptionally well insulated, keeping it the same temperature as the rest of the house, making it pleasant to walk on. The attic was designed with lots of space for insulation, so it was easy and affordable to pile it up to R-100. This entire home is heated with a single electric heater, the size of a large toaster, installed in the air supply duct. Avoiding paying for a regular furnace made up for a lot of the cost of the extra insulation.

FLeX House. Photo Credit: US DOE

How Much Insulation Does a High-Performance House in a Hot Climate (Zone 8) Need?

Sound insulation is also crucial for homes located in hot climates. While good ventilation can certainly help to cool a home in a hot climate naturally, insulation can play a major role in keeping the cool, conditioned air inside the home when temperatures rise to the triple digits. The Passive House Planning Package recommends that builders understand the solar loads and the ventilation strategy. This way, you can ensure that temperatures inside the building do not exceed 25°C for more than 10% of hours annually.

In an article titled The Passive House in Summer, Wolfgang Feist states that "insulation does not create any additional heat; it only reduces the heat exchange between systems with different temperatures. Therefore, it also protects a cool system from gaining heat from the surroundings."

The FLeX House, in warm and sunny Florida, is an excellent example of a super-insulated home in a hot climate. Besides incorporating insulation that exceeds the code minimum, the house also utilizes passive solar orientation and an internal dehumidifier with a desiccant system to take moisture out of the indoor air.

Insulation Rolls

To build today's top energy-efficient homes, you need to use substantially more insulation than the minimum code, especially in cold winter climate zones. The payback for that investment is three-fold – superb home comfort, astonishingly low energy bills, and energy security.

A beautiful feature of these homes is that, even in an emergency involving an extended power outage in winter, they cannot freeze on the inside. Because they are so well insulated, even the sunlight that comes in daily through the windows is enough to keep them safely warm. That means your home's interior and water systems are protected from freezing under all circumstances, whether you are home or away.

Disclaimer: This article does not constitute a product endorsement however Rise does reserve the right to recommend relevant products based on the articles content to provide a more comprehensive experience for the reader.Last Modified: 2022-01-19T03:20:01+0000
Tobias Roberts

Article by:

Tobias Roberts

Tobias runs an agroecology farm and a natural building collective in the mountains of El Salvador. He specializes in earthen construction methods and uses permaculture design methods to integrate structures into the sustainability of the landscape.