Building for the Chemically Sensitive

Those who are building and have moderate to severe chemical sensitivities have a number of factors they need to consider in the very early stages of the planning of the build. You could easily end up between a rock and a hard place without considering these details in advance. I have seen it many times!

It's incredibly important to build in a mold-preventative manner in order to recover in the new house, and it can at times be difficult to balance those two needs together. So the following areas to consider also apply to those building for mold prevention.

Here are areas that must be considered in the very early stages of planning a house if you are chemically sensitive:

"Sv sava topography P.Cikovac" by Orjen is licensed under CC BY-SA 4.0 


1. Climate

Before you draw up plans for your house, you need to know the location primarily because you need to know the climate zone. This will impact your design significantly. This can impact your foundation type (and many who are building mold preventative want to use a specific type of foundation), it will also impact insulation requirements - with many areas in the US starting to require exterior insulation, you need to know if you can tolerate Rockwool Comfortboard, rigid sheathing or cork, for example. It will impact many other materials choices as well as HVAC system requirements.

If you are deciding between two cities or towns we can still start to put your materials list together and see if that impacts the type of house you can build in each area.

2. Topography

The exact piece of land can impact the design as well, since you will look at the topography of the area and site itself, and how that will impact the design - this could influence the size and shape of the house for example, as well as how the crawl or basement is designed, where you will place the garage etc. This is also important to factor into your budget. If you have a slope or are creating a hill for the house drainage it will impact costs as well as the lot size (distance you need from other houses/property lines). Though you could work the other way around, pick land that is flat enough and large enough to fit your design.

3. Building Codes

Another reason you will want to know the location, including possibly the exact location, is because building codes and neighbourhood requirements will impact which materials you can use. These could be codes around things as major as the minimum size of the building, and as small as the type of plumbing you use, for example. Those with MCS are often on a budget and want to build small, and you will almost certainly have materials that you have to be rule out due to sensitivities.

4. Neighbourhood or HOA Requirements

Neighbourhood requirements can impact facets of the build like the type of siding that is required. In some historical areas wood siding is required, sometimes even a specific type of wood. Wood siding is not the most durable option for rot prevention, and those with MCS may need to avoid certain types of wood (like cedar). There are areas where roof types are dictated by the local requirements, this could rule out a metal roof (which is what most with MCS want to use). There are areas that require flat roofs (though you can make it look flat usually and meet that requirement). Those are just a few examples.


1. Wood Framed House?

At this point in the process you will need to have an idea of what materials you tolerate. The more info you have on which materials you tolerate the better. Most who are sensitive to wood are not sensitive to wood when it's in the walls - but you need to know which category you are in. You need to know if you are designing a wood framed house or something entirely different! If you are avoiding wood altogether you may want to consider other climate appropriate options which could be metal and foam, metal SIPS, adobe, hempcrete, concrete, and insulated forms. I discuss alternative walls systems in this post. The post on tiny homes talks about some other unusual systems. An upcoming post on (regular sized) prefabs will cover more alternative systems. Choosing the materials that are tolerable and healthy for you is one of the main things we will cover in a one on one consult.

2. Plywood and OSB?

While many with MCS want to avoid plywood and OSB, avoiding those two items will create a lot of "work around". You may be able to use alternative sheathing, or you may have problems with code, you may have a much more expensive house, or you may in the end have to go with a totally different type of house than a wood framed one. I encourage those with MCS to read through this post on plywood and OSB before ruling it out. I help folks go through these areas of the build that they have to consider, test options, and weigh the pros and cons of the alternatives. There are ways to offgas and even seal plywood which could in the end save a lot of money and worry.

3. Insulation?

You should also have an idea of which insulation you can tolerate. This is another main area that comes up in every session. Your typical build has rigid foam in the slab, breathable insulation batts in the walls and depending on the design and climate, spray foam in the attic. If you need to avoid spray foam insulation (which in general I would), you need to make sure your design takes that into consideration.

With batting, go through the options in the insulation post, as those are the ones we will go over in a consult. If you cannot tolerate any of the insulation batts, again, this will dramatically change the type of house you build.

"WALLTITE spray foam insulation being applied" by Cdpweb161 is licensed under CC BY-SA 3.0 


Decisions that impact the design

1. Avoiding Spray Foam

If you don't tolerate spay foam insulation make sure to design a roof and foundation that do not require it.

2. Avoiding Laminated/Engineered Lumber

If you want to avoid laminated/engineered lumber to avoid extra glues (see this article to see what I mean), this has to be considered very early in the design. You can only span so far with traditional lumber.

3. Avoiding Ductwork

If you want to avoid all ducted HVAC due to extreme mold sensitivity, this has to be factored into when designing a house. (If you want to avoid AC altogether due to sensitivities, that part definitely has to be factored into even earlier into the location. Even if you don't mind hot temperatures, you have to look at summer humidity since AC brings down humidity).

4. Design Areas to Consider

Consider simple roof designs to cut back on where things can go wrong, consider large overhangs to protect the walls, simple floor plans can help with cost reduction, carefully design plumbing in an interior wall that has access panels.

5. Avoiding Toxic Windows

You need to design the house around the windows! Yes this is that important of a factor. Many super chemically sensitive folks have run up against this problem too late in the build. First, the very  sensitive will want to go with aluminum windows (see my post on windows), and those can only be found in certain standard sizes (unless you go for totally custom, very expensive windows). Aluminum windows are already expensive. If you don't design around those sizes you are going to end up with either windows that you don't tolerate potentially (fiberglass, vinyl), reframing the house (big expense), or custom windows (another big expense).

"House Plans: Front" by Fugue is licensed under CC BY-SA 2.0 


1. Testing Materials

In order to not delay the build you want to make sure you have tested out all the materials needed down to the caulking, glues, sealants, grouts, thinset, and all the major materials as well. What can happen here is that if you need to make a substitution, some items are special order and need to be considered early on. You don't want to delay the project with special orders and you also don't want to delay the project because you need more time to test out materials.

If you are extremely sensitive you will either be factoring time in for the house to offgas before you move in, or possibly building a type of wall system that limits the types of glues, caulks, tapes that you are reactive to (alternative wall systems are listed here).

There are certain corners that cannot be cut while trying to eliminate offgassing. I've seen it done a lot in houses built for the extremely chemically sensitive. But long-term, you cannot cut corners on the integrity of your building system which is designed to keep out water, moisture, and air. Preventing mold is very important for those with MCS.

You want a builder who understands when materials can be substituted out and when they can't. Some builders will do whatever you want done because they don't have a high degree of understanding of building science, and so they don't know why that will fail. Or they may be too rigid and reluctant to change anything, again because of lack of knowledge of how to keep the integrity of the system while doing something slightly different. I will work alongside your architect and builder to make sure that the right compromises are made.

2. Contracts

Make sure the builder understands your level of chemical sensitivity and how important this is. You need to have certain requirements here in your contract to protect your site and your build. Paula Baker Laport outlines this in her book Prescriptions for a Healthy House.

You also want to work with your architect to produce a contract that will help protect you on the mold-preventative building front.


1. Your Architect

An architect is needed in any build to help design the moisture management systems. An HVAC specialist will likely be needed if you are doing a ducted system (or any other complex system). When looking for an architect, you need someone whose specialty is mold prevention and/or high performance systems like Passive House.

Anyone who has a high commitment to design and details that prevent moisture problems, rot, decay, and mold is what you are looking for. This can be worded as fine craftsmanship, high performance, increased durability and similar terms which are geared at the non-sensitive. These builders do higher quality work, their houses cost more and they have to market this to the general public as high performance or durability.

2. Your Builder

The same thing goes with a builder. A builder should be highly skilled, highly detail oriented, a perfectionist with getting the details right, someone who understands building science and has an interest in it. A good problem solver, can think outside of the box to accommodate you, while also understanding any repercussion of going too far against the norm.

The builder should have total buy in to the idea of building to accommodate your sensitivities and be thoughtful and mindful so that the wrong products are not brought in accidentally, in a hurry or to clean something up.

You builder should also be highly cooperative with your architect and with you (or your supervisor).

Highly skilled builders will be interested in building a well planned and very well executed house and will not have a problem with working with your architect and you to get it done right.

If they are not used to building high quality work, this will be a battlefield.

You can find a good builder through a good architect or you can find one on your own who you like. When I see high quality builders I list them here (though I don't know all of them well, and they are only as good as the weakest labourer or as good as their supervision).

Please get in touch if I can help you through the process, especially to make sure you know which materials are best for you so you can design your house around it. And we will make sure you have the right experts to build a high quality, mold-preventative, low offgassing home.

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