No, you do not need foam board under vinyl siding. Most building codes do not mandate it, and you can install siding directly over a properly prepared, weather-resistant housewrap.
Most homes have a combination of materials behind vinyl siding, including plywood or OSB (oriented strand board) for structure, a weather-resistant barrier (like house wrap or felt paper) for moisture protection, and foam board for extra insulation.
These include:
DuPont™ Tyvek® weather barriers can be used either over or under sheathing. When Tyvek® is used under sheathing, it functions only as an air barrier, and does not protect the sheathing as a secondary weather barrier.
Rigid foam insulation is an insulated sheathing foam that's denser than fiberglass or cellulose. Also known as rigid foam board, this type of insulation is great for cold climates because it's not affected by moisture like fiberglass batts are.
Tape the seams and you've got all the benefits of an air barrier, a WRB, and a thermal break. But it doesn't have the benefit of keeping the sheathing warm. Just something to be aware of.
Because spray foam can trap moisture, hide the condition of the roof, make it difficult for surveyors to inspect, which means risks like timber decay, dry rot, and not forgetting increased fire risk. If you've got it or you're buying a property that does, this is something you need to know upfront.
Foam insulation is a common target because it's easy for them to chew through. The material offers little resistance, allowing mice to create tunnels or nests within the insulation. But mice aren't just interested in chewing for the sake of it—they're also drawn to the warmth and shelter insulation provides.
In general, if the foam rigid insulation is installed correctly and sealed properly, a vapour barrier may not be necessary. However, there are certain situations where a vapour barrier is recommended, such as in areas with high humidity levels or where there is a risk of moisture infiltration.
Natural Smells the Amish Use to Repel Mice
Traditional methods often include using natural deterrents like peppermint, pine, or other strong plant-based smells. Whether it's growing plants near entry points or using oils indoors, these scents can interfere with how mice navigate and make the space less appealing.
This movement of mice and rats to find shelter indoors is known as rodent season. It can begin as early as August or as late as October depending on where you live and the weather conditions in a given year.
Ammonia. Ammonia is one of the stronger scents mice hate because it gives off a smell similar to predator urine, which can signal danger. Homeowners sometimes place small dishes of ammonia near entry points or in areas where mouse activity has been spotted.
Disadvantages of Tyvek® House Wrap
Tyvek® House Wrap has a tensile strength of only 30/30 lb/in. So, after installation, but before the exterior cladding and final fasteners, Tyvek® House Wrap may be susceptible to damage due to high winds and moisture exposure.
You may love your home with purple siding and orange trim, but potential buyers may not feel the same way. There are several siding colors that offer the best resale value for your home, including light neutrals, blues, grays, light browns, white, neutral greens and tans and earth tones.
The by-the-book answer to your question is that vinyl siding manufacturers require a flat, solid supportive surface, and limit foam installed under their siding to a maximum of 1 in. thick. So, technically speaking, you can't nail through or even use 2 in.
Disadvantages of polystyrene foam insulation board
Expanded polystyrene foam boards are made with air bubbles that stop heat transfer. Unfortunately, those same air bubbles collect moisture which leads to mold and mildew growth. Solution: Rigid foam board insulation products are actually made to be water resistant.
In heating-dominated climates, the vapor barrier under concrete slab should be placed above the insulation—between the foam and the slab. This keeps the barrier on the warm side of the assembly, preventing condensation from forming within or beneath the insulation.
Key takeaways
Some common rodent-proofing methods include:
Using thick concrete, sheet metal, brick, or hardware cloth to seal larger gaps.
The number one killer to mice is rodenticide, a type of poison designed to eliminate them quickly and effectively. These poisons work well but can harm pets, kids, and wildlife if mishandled. Mice may be small, but they can cause big problems inside homes and businesses.
The issue stemmed from older homes being retrofitted with spray foam insulation in the roof line, leading to moisture buildup and potential rot issues. The lack of a vapor barrier and inadequate insulation thickness contributed to the problem.
Direct contact with fiberglass or breathing airborne dust containing fiberglass may irritate the skin, eyes, nose, and throat. The symptoms of irritation are often nonspecific, temporary, and may include itching, coughing, or wheezing.
Contrary to the myth, properly installed spray foam insulation does not promote mold growth. It acts as a moisture barrier and can help prevent moisture intrusion when combined with proper building maintenance and ventilation practices.