Overview

Factory-built modular homes must meet energy requirements that account for their completed construction, including the connections made between sections on site. In this blog post, Well Built Construction explains how BC’s energy standards influence modular home manufacturing and installation, along with the testing used to verify the finished home’s performance.

Highlights

Introduction

A modular home can arrive with finished walls and much of its insulation already enclosed, but the connections between its sections still have to be completed on the property. Properly sealing those joints and installing the specified heating and ventilation systems determine whether the assembled home achieves the energy performance established during design. Here’s what you need to know.

What BC Energy Standards Apply to Modular Homes?

The BC Energy Step Code sets efficiency targets for new modular homes built under the BC Building Code. The required Step depends on where the home will be installed and when its building permit is issued. A modular home builder uses that target to select wall assemblies and heating equipment before factory construction begins.

Step 3 is the provincial minimum for most new small residential buildings, though municipalities can require higher steps. The separate Zero Carbon Step Code sets requirements for emissions from operating a home, with stricter levels influencing fuel choices for heating. Builders need to verify both levels with the local building authority before finalizing the home’s specifications.

Common problems that can prevent a home from meeting its energy target include:

  • Window performance: Large areas of glazing with poor insulating properties can increase winter heating demand.
  • Heat escaping through framing: Framing can conduct heat through a wall even when insulation fills the spaces between studs.
  • Unsealed joints: Gaps where factory-built sections connect can allow heated air to escape after installation.
  • Changes to heating systems: Installing equipment different from what the design specifies can affect the home’s expected energy use.

The Step Code evaluates the overall design, so larger windows can be balanced with better glazing or additional insulation elsewhere in the home.

How Does Factory Construction Improve Energy Efficiency?

Factory construction lets builders install insulation while wall framing is still exposed. Corners and openings for utilities can be checked before drywall goes up, when gaps are easier to correct without cutting into finished surfaces.

Indoor production protects unfinished assemblies from rain and allows workers to follow the same construction details across multiple sections. Each stage can be checked before the next layer is added, helping crews catch inconsistent insulation or sealing work before it’s concealed.

Factory construction practices that support energy performance include:

  • Fitting insulation: Materials are installed snugly around framing to avoid empty spaces that allow heat to escape.
  • Sealing penetrations: Openings around cables or pipes are closed using materials compatible with the specified air barrier.
  • Checking window openings: Properly installed flashing and seals protect the joints around factory-fitted windows.
  • Inspecting concealed work: Air-barrier details can be checked before drywall or exterior finishes cover them.
  • Protecting modules: Exposed edges are secured for transport so insulation and seals arrive intact.

How Does Airtightness Limit Heat Loss?

Warm indoor air escapes through small gaps in the walls and is replaced by colder outdoor air that the heating system has to warm. A continuous air barrier reduces that exchange by sealing the openings where air would otherwise move through the home’s outer structure.

In a modular home, taped sheathing or a sealed membrane can form that barrier, depending on how the wall is built. Crews connect it around plumbing penetrations and at joints where walls meet the roof or floor.

How Is Energy Efficiency Maintained During Installation?

Factory-installed insulation and air-sealing layers can be disturbed during loading or highway transport. Before the modules are joined on site, installers check their exposed edges for shifted materials and restore any damaged seals that will become inaccessible after assembly.

Foundation connections require properly fitted insulation because gaps at the base of the walls can leave the floor cold. In homes built over an unheated crawl space, crews insulate the rim joists along the floor’s perimeter and seal adjoining surfaces. For a slab foundation, edge insulation helps reduce heat loss through the concrete, while basements require insulation suited to their foundation walls.

Once the modules are placed, crews finish any site-built roof sections and exterior transitions. The roof insulation must join the factory-installed material without gaps, particularly where adjoining sections create cavities that won’t be accessible after the ceiling is finished. Otherwise, the connection can become a continuous area of heat loss across the home.

How Are Gaps Between Home Modules Sealed?

The joint where two modules meet, commonly called a marriage line, can run through adjoining walls and across portions of the roof or floor. Insulation placed within that joint limits heat transfer, while a separate continuous air barrier prevents warm air from passing through the seam.

Installers connect the designated membranes or sheathing joints, then complete exterior weather-resistant details that keep rain away from the concealed assembly. The sequence needs to follow the specified wall and roof design so the joints can dry as intended.

Plumbing and wiring that cross the marriage line leave openings that must be sealed at the designated air barrier. Closing the visible drywall seam won’t stop air from escaping through a gap behind it. Air moving into a cold wall cavity can also carry moisture, which can condense on cooler surfaces and damage concealed materials over time.

Which Mechanical Systems Affect Energy Compliance?

Space-heating equipment accounts for a significant share of a modular home’s energy use during winter. A heat pump generally supplies more heat per unit of electricity than an electric resistance heater, though its efficiency usually decreases as outdoor temperatures fall. Cold-climate models are designed to maintain useful heating output in lower temperatures.

Heating systems should be sized using the home’s calculated heat loss rather than its floor area alone. Oversized equipment can cycle on and off too frequently, while an undersized system can struggle on the coldest days. The calculation accounts for the home’s actual insulation and window performance, helping builders select equipment suited to the finished construction.

In colder parts of BC, energy calculations account for backup heating when a heat pump can’t meet demand. Water heating contributes to overall energy use, with heat pump water heaters typically consuming less electricity than conventional electric tanks.

How Does Heat Recovery Ventilation Work?

A heat recovery ventilator, or HRV, brings fresh outdoor air into the home while exhausting stale indoor air. The two streams pass through separate channels in a heat exchanger, where outgoing air transfers some of its warmth to the incoming air without mixing the two.

After installation, crews balance the ducts so the intended rooms receive fresh air. In colder weather, the HRV reduces the heating needed for that incoming air, and some models run frost-control cycles to prevent ice buildup in the heat exchanger.

How Is Modular Home Energy Performance Tested?

Before the home is manufactured, an energy advisor uses its plans to estimate how much energy it will need. The calculations account for insulation and window performance, along with the planned heating equipment, to determine whether the design meets the required energy target.

The results serve as a reference during manufacturing and installation. If a different window package or heating system is chosen after the design is approved, its impact should be checked before the replacement is installed.

After installation, the home’s measured airtightness and any changes to the approved construction details are recorded for the building authority. Factory inspection records document work concealed before delivery.

What Does a Blower Door Test Measure?

A blower door test measures air escaping through unintended openings in the completed building enclosure. A calibrated fan temporarily creates a pressure difference between indoors and outdoors, while instruments record the airflow needed to maintain it.

Testing the assembled home can reveal leakage at module connections even when individual factory sections were carefully sealed. If results fall short of the required airtightness level, technicians can identify leaks and seal them before another test.

Results are typically reported as air changes per hour at a standardized test pressure, allowing the measured leakage to be compared with the applicable airtightness target.

How Do Higher Energy Standards Improve Indoor Comfort?

A well-insulated wall keeps its interior surface closer to the room’s air temperature during winter, reducing the chilled feeling people experience near poorly insulated walls. High-performance windows help in a similar way, particularly where large areas of glass would otherwise feel cold to anyone sitting nearby.

Warmer interior glass reduces the chance of condensation on cold mornings, though high indoor humidity can still cause moisture to collect. A higher energy Step doesn’t eliminate the need for proper ventilation.

Large west-facing windows can admit enough afternoon sunlight to overheat a room, even in a home that meets a high energy Step. Exterior shading blocks much of that heat before it reaches the glass, while appropriate window specifications can limit the remaining solar heat gain and reduce the cooling needed in summer.

Build an Energy-Efficient Modular Home in BC

Well Built Construction manufactures modular homes and cottages in its factory and assembles them on your property as a licensed residential builder, carrying energy-efficient construction details through to final installation. Call (250) 826-2284 to arrange modular home construction and installation in British Columbia.