Build Science: My house

Purpose of this document

1. Document desired construction details (function only, not form)
2. Am fully aware that many compromises will need to be made :/
3. Am completely open to anyone convincing me any of these ideas are wrong :)
4. Reduce stress by getting ideas on paper 🧘🏻

Credit: Matt Risinger

• The build show
• Youtube

Priorities driving all goals

1. Keeping water where it belongs
2. Ability to dry
3. Ability to monitor/maintain/repair
4. Optimize compromise on things easier to change later
   • e.g. zero compromises in the foundation (plenty in the finishes)
5. Energy efficiency is not expressly a goal
   • Am not trying for passive house

Foundation

The foundation is the most important aspect of the home (and the most difficult to fix later)

Have someone knowledgeable review this particular section:)

Goals

1. Obviously strong enough (will leave this to the professionals)
2. Minimize possibility to get wet (leading to rot)
3. Ability to dry when wetting invariably occurs
4. Minimize ability for critters to get in there
5. Make it easy to identify and kill things
6. Clean air, as it will ultimately make it’s way into the house above
7. Easy to access, with good lighting and electricity - so it gets checked regularly

Ideas

1. No radon gas (but is measured if appropriate)
2. Liquid applied water sealant (to exterior of stem wall and footing)
3. Dimple mat to reduce hydrostatic pressure and encourage drying (dimples facing the concrete)
4. Layer of thick poly under the slab for waterproofing
5. Insulation under the slab and exterior to the walls
6. Curtain drain exterior to the footings, with angled clean-out(s)
   1. Made of PVC, holes up and down (not the flexible kind, difficult to clean)
   2. Around entire foundation - all sides
   3. On top of smooth gravel bed
   4. Covered by filter fabric of some kind
   5. Covered by way more smooth gravel
      • Exterior to insulation
      • Up the entire height of the stem wall
   6. Drained to daylight (East)
7. Installed dehumidifier to guarantee measured dryness (and drains via tubing)
8. Installed water sensors - we need to know if all efforts failed :/
9. No air sealing or insulation under the floor joists. More difficult and reduces access to plumbing, invariably needed later :/

These requirements can only be satisfied by one of two choices:

1. Full basement
2. Encapsulated crawl space with at least 4 feet of height (preferably 5)
   • This means conditioned (identical air quality as the house itself)

This means the only variables are:

1. Height of stem wall (and possibly size of footings for PSI)
2. Presence of full slab, rat slab, or just dirt/rocks and sealed poly

Open questions

1. How to terminate the poly under the slab at the footings? Should it extend under the footings themselves?
2. Should the poly go above the insulation, to ensure it doesn’t float in the wet concrete?

Roof

The roof is the second most important feature, second to the foundation.

Goals

1. Make it safe to access and easy to clean
2. Effectively shed water to a desired location
3. Include minimal penetrations (to reduce likelihood of failure)
4. Ability to dry when wetting invariably occurs
5. Minimize ability for critters to get in there
6. Heavily insulated (to move the condensing surface outside the envelope)

Ideas

From the inside out:

1. Appropriate weather membrane
2. Exterior insulation (to move the condensing surface further out)
   • Really want mineral wool (solid performance, fire resistance, hydrophobic, etc)
   • Prefer not to have Polyisocyanurate (polyiso) due to it’s weakness below 50° F
     • Do I want to avoid this enough that Zip-R is ruled out?
   • Prefer not to have Extruded Polystyrene (XPS) due to off gassing and performance loss over time
3. Eave framing external to the insulation
   • This is to ensure the best performing WBR over the roof ➙ wall transition
4. Vertically oriented battens to provide air gap below the metal (to allow condensation and wood to dry)
   • This is to ensure stack effect can do it’s thing
5. Horizontally oriented battens to provide nail surface for clips
6. An air gap at the ridge (if there is one, ideally there isn’t)
7. Bug screen at perimeter to protect the air gap
8. Closed (or ideally non existent) soffits
9. Standing seam metal (clip system)

TODO: Research and consider a butterfly roof?

Open questions

1. Should the horizontal battens have a second layer of sheathing on top? This would ensure the metal can’t bend when walking on it (reduce oil canning, etc)
2. Given the presence of exterior insulation will increase the effective R value of the entire assembly (am assuming will be 12" members, so R-36), how much exterior insulation should I want? This stuff is super expensive. Is R-50 the goal?

Windows

Goals

1. Minimize water getting where it doesn’t belong (leading to rot)
2. Ability to dry when wetting invariably occurs
3. Ability to resist getting foggy over time (not sure what causes this)
4. Easy to maintain (e.g. screens that aren’t impossible to clean, casement?)

Ideas

1. The window sill needs to be tilted a little bit, so the water drains away
2. All sides of the window need a custom waterproof pan created
3. The window should be held off the sill by shims (so it can dry)
4. The window should not be caulked near the outside of the bottom, so the water can run out
5. Detailed with bucks to accommodate exterior insulation
6. Ideally aluminum or fiberglass for durability
7. Reference:

Exterior wall assembly

Goals

1. Minimize possibility to get wet (leading to rot)
2. Ability to dry when wetting invariably occurs
3. Be considerate of exterior insulation on the trades
   • For example any exterior panels would need insulation added well ahead of the rest of the house (emphasis on order of operation planning)

Ideas

1. When water gets behind the cladding (which it will), it needs a way to dry. Having an air gap followed by vapor open materials followed by a waterproof membrane - the entire assembly can dry to the outside.
2. Bug screen behind the cladding at the bottom
3. The weather membrane selected must be vapor open.
4. The inside walls are very difficult to air seal perfectly. This means any warm humid air that leaks through the inside wall assembly will touch the sheathing, which could be cold - and condense on the backside of the sheathing. The solution here is exterior insulation, in addition to the vapor open (but air tight) membrane on the outside of the sheathing. The two will keep the sheathing warm, with minimal air flow.

Note:

• My current thinking is to use a dedicated WBR even if Zip is used
• This image is just an example, am open to ideas

Plumbing

Goals

1. Minimize possibility of leaking (reducing fittings, etc)
2. Minimize damage when leaking occurs
3. Ability to decrease re-pipe cost/effort when leaking invariably occurs

Ideas

1. Water pans with sensors under all sinks, plumbed appliances, etc
   • The pans and sensors don’t need to be fancy, will test them
2. Maximum amount of exposed pipe/fittings (monitoring and re-pipe friendly)
3. Nail guards (am assuming these are code)
4. Manifold system for ability to turn off specific runs when they fail?
5. Potentially have a loop system to reduce water waste on the HOT side
6. Pex (type B, Uponor, Zurn)?
   • If these jokers really have a 25y lifespan, absolutely zero chance I want to bury it in concrete (radiant flooring)

Open questions

1. What the heck to think of the Pex class action suit?
2. Does the lack of a wax ring on a wall mounted toilet make it worth the cost?

Ventilation

Goals

1. Ensure everything has a direction it can breath
2. Maintain prescribed humidity inside the envelope (the rest is outside the WBR)
3. Maintain healthy dose of fresh air
4. Provide mechanism to protect the family in smoke season?

Ideas

1. Can have multiple air barriers, but only a single vapor barrier (if any)
2. Energy recovery ventilation (ERV)
3. Humidity and temp sensors