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Need feedback for off grid building-humidity and basements???

 
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Hello! I have stalked the permies.com forums for years, and we are in place now to begin building. Our land and the opportunity to build came upon us quite suddenly so we are not as prepared and thoroughly researched as I wish, and we do need to get the project underway pretty quickly. We have a large family, so as much as I adore the idea of tiny-we need about 1500 sqft of space for our family realistically. My desire was to just go as "amish" and old school/simple in building as we can, but we do have a family member with asthma who does poorly at times with the hottest and most humid days and we have to avoid mold at all costs as well, and we need to be able to cool the home a bit for them or have a small unit to sit in front of if need be. I have researched earth tubes as well, and we will be on a hill-but I am concerned with the condensation in the tubes and do not want to be reliant on a mold/mildew cleaner every month to ensure we aren't bringing in moldy air. But the idea is so lovely, with a solar chimney or whole house fan-I just don't know how to make it work exactly for our SE America environment. I need thoughts with that please.
We have a great spot picked out-we will get full-shade on the house with a grove of beautiful oaks to our west, for afternoon heat relief. It's on a windy hill so ventilation should be good. We have been trying to decide if a walkout/partial basement on this hill (south facing), coupled with a more "airy" feel upstairs (not super airtight construction, windows open often, etc), would result in a horribly moldy mess during humid summer time in basement. I initially wanted to build up on short stilts to mimic the traditional construction you find in places like the Smokies, and it would allow plenty of air circulation underneath the home, with the intent to insulate the minimal water pipes. We were thinking of avoiding AC, instead installing a whole house fan and drawing in air from the cooler shaded north side and west, but I'm afraid with a walkout basement, when we open windows to get that airflow in the summer-we will get nothing but condensation in the basement (which would be well ventilated itself with no closed off interior walls-just an open living/rec room space that we hope is a little cooler of a space than upstairs in the July-August time frame).
Years ago we remodeled a 100 year old home and loved the concept of the balloon wall construction (it was wood siding, wood boards inside- the whole "shiplap" look, with a few inches of unobstructed empty space between,all the way up the wall to vents in the side of home for the chimney effect, along with the whole house fan that they had installed at some point, silver reflective roof, all living spaces to south for plenty of light, with rare need for artificial light, deep west facing porch, bedrooms on northside were always cool, etc... Just lovely. We want to combine as many of these wise historical elements as possible. We will have a small solar array, a shaded cool concrete or light brick patio outdoor kitchen to the north for summer cooking/canning and laundry, our bathroom and mud laundry porch in a well ventilated lean to-to minimize the moisture from laundry and showers. My kitchen will have the sink and oven on an exterior wall for moisture ventilation right outside. No dishwasher. Hubs thinks walkout basement will be ventilated enough to not worry about the condensation and mold, though I think it will also not become as cool as would be desired because south facing-so it may not be a big deal.
I also love the idea of using elements of the dogtrot house-with a central sheltered gathering space that can be opened for breeze, separating living spaces from sleeping spaces. But I'm new to that thought. Winter heat and cook with wood (we have plenty). Sorry so long! Thanks for your thoughts!!
 
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Interesting project.
I looked up balloon framing, not having heard of it. balloon framing explained
It has a single problem. You need to install 'fire blocks' between the studs at the top of the lower room, they prevent fire racing up the inside of the walls.

I think with the use of materials not available in the early days, large windows for a start, the venting system you describe may be not needed.
A day or so ago I added to a topic discussing natural ventilation, I will find a link. /Air-flow-design-house , this discussion was around a hot dry climate.
If you study buildings in Malaysia or Queensland  [ Australian state ]  for instance you will get ideas.
The Queenslander is a building style, using tall stilts to support the house, wide verandas and louvre windows and slats to control air flow and sunlight.
A Queenslander is no good if it snows, so what is your year round climate like?

Here are some statements;
- A natural ventilator, supported by intake air supply, allows humid air to rise and out of the building. In conclusion, proper ventilation is the key to reducing humidity.
- Natural ventilation can draw unwanted warm air out of the room towards the outside and so let fresh, cooler external air flow in. In the cool night-time period, free ventilation provides natural building climate control.
- In a hot and humid climate, the orientation of the buildings should be along the long axes in the east-west direction.
 This will eventually place the longest façade in north and south direction along with a short wall facing the east and west direction
- What is the best building material for humid weather?
 The best materials for humid climates are engineered hardwood, spray foam insulation, clay or lime plasters, proper windows and ventilation, waterproof paint, and sealants.
 Concrete can be used in humid climates, but excellent humidity control needs to be established as well.

warm-humid-climate-house-design/
-
download-1.jpg
a Malay design concept drawing
a Malay design concept drawing
 
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I will echo ventilation being good for dealing with humidity.

If you can get a full cross-breeze through any room ventilation is as easy as opening up windows on both sides of the house.
 
L. Johnson
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Also, in Japan traditionally interiors were finished with a natural plaster called shikkui. It has some very useful properties for managing humidity.

https://en.wikipedia.org/wiki/Shikkui
 
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Welcome, and a good first post! I live in a house with cinderblock walls on the lower floor and concrete floors. Two walls are set into a hill such that you can step onto the roof from the ground. This past summer, I decided to try to forego the air conditioning all summer as long as it was not unbearable. The hottest it got on the lower floor living area was 80F degrees. This is in Kentucky. It was not bad at all. I decided a good indicator would be if my dog panted inside while at rest, it would be considered too hot, and he never did. I also felt healthier and not fazed by the hottest part of summer, though I have always preferred the heat to the cold. I have come to believe going in and out from hot to cold is not good for the system.

Mold was a constant battle. I learned that beeswax can mold. Unfinished wood molded. Linseed oil treated wood really molded. Wood finished with shellac did not. Keeping flour long was not a good idea. I have always had to deal with mold, but not like this. In the past, I usually kept the air conditioning cooler than I really preferred, not for coolness, but for dehumidification. Without it, I have faced some 95% humidity inside. Partly because cooling hot humid air makes cooler, more humid air, and partly (I believe) due to the concrete's desire to absorb water from the ground. I would hope natural building materials would not be as bad as portland cement, but I have a feeling  humidity is just going to be an issue where I live.
 
John C Daley
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Jordan, I would look at sealing the concrete wall so moisture cannot come from the ground into the basement.
Its not always a good idea, but perhaps study the situation.
If better ventilation was near that wal t may improve
 
Anna MacLeish
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We are in the Appalachian area of TN, so we do get snow in winter-though not much. But plenty of below freezing nights in winter for a couple of months, and hot humid days in summer. It does cool off at night even in the summer, which also brings up my concern with mold. In the morning, plastic chairs on the lawn are caked in dew, and I don't want that happening anywhere inside the house.
 
Jordan Holland
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John C Daley wrote:Jordan, I would look at sealing the concrete wall so moisture cannot come from the ground into the basement.
Its not always a good idea, but perhaps study the situation.
If better ventilation was near that wal t may improve



Thanks, John! Unfortunately, the wall is not accessible. Some of it would be with some laborious work, but some still wouldn't be. The kitchen and bathroom came with those new synthetic floor tiles, and I used ceramic tiles in the bedroom and bathroom. The living room has a wood floor with a plastic vapor barrier under it. I would have expected this to make a dent in the humidity, but it doesn't seem to much.

Ventilation is only at night. Ventilation during the day would mean more heat. Drawing air from the north side of the house wouldn't help keep it cool much when it's 95 degrees outside. And bringing in more humid air to cool down (if the house had enough heat sinking ability to do it) would also be bringing in more moisture. I think not much can be done, but I believe if vapor barriers were used to completely isolate the house from the ground before construction, it should help, but ultimately I don't know how much moisture is coming from the ground and from the outside air.
 
John C Daley
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Dew on the chairs is another phenomenon, of nature.
Snow would drive you out of the houses I suggest!
 
pollinator
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Hey,

This is an awesome and very important question,


In my experience working on renovating and restoring federation Homes,

I have looked over the following ideas,

the rocks, bricks, cement wiking up moisture, needing a barrier to prevent this, Paul wheaton uses builders black plastic sheets.
which also helps with termites, so its good, if it does not break,

airflow,
Having cavity brick with the vents having bricks behinds them,

water not being able to move away, Lack of spoon drains, gutters, seepage holes,


People have added fans to under houses to move moist air away,

also people have suggest increasing agg-pipe and aggregate and membrane drainage,  adding sumps around houses, which is good so long as it all is bellow the depth to prevent water from moving under the home,

One thing I was sure to do was buy a moisture metre, and always check the fireplaces,
they sink and crack, cause movement, it is a target spot of moisture, plus another issue is water coming down chimneys, I measured 80ml in one over 1 hour. in strong rain.

Basically all the humidity controlling aspects of a greenhouse are useful, plus thinking about ground water wiking up bricks and decaying mortar, and thinking of the hydrology of the soil around your property!

You may consider using a damp course product but this will only be guaranteed to work for 5 years or so!



 
Alex Moffitt
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John C Daley wrote:Interesting project.
I looked up balloon framing, not having heard of it. balloon framing explained
It has a single problem. You need to install 'fire blocks' between the studs at the top of the lower room, they prevent fire racing up the inside of the walls.

I think with the use of materials not available in the early days, large windows for a start, the venting system you describe may be not needed.
A day or so ago I added to a topic discussing natural ventilation, I will find a link. /Air-flow-design-house , this discussion was around a hot dry climate.
If you study buildings in Malaysia or Queensland  [ Australian state ]  for instance you will get ideas.
The Queenslander is a building style, using tall stilts to support the house, wide verandas and louvre windows and slats to control air flow and sunlight.
A Queenslander is no good if it snows, so what is your year round climate like?

Here are some statements;
- A natural ventilator, supported by intake air supply, allows humid air to rise and out of the building. In conclusion, proper ventilation is the key to reducing humidity.
- Natural ventilation can draw unwanted warm air out of the room towards the outside and so let fresh, cooler external air flow in. In the cool night-time period, free ventilation provides natural building climate control.
- In a hot and humid climate, the orientation of the buildings should be along the long axes in the east-west direction.
 This will eventually place the longest façade in north and south direction along with a short wall facing the east and west direction
- What is the best building material for humid weather?
 The best materials for humid climates are engineered hardwood, spray foam insulation, clay or lime plasters, proper windows and ventilation, waterproof paint, and sealants.
 Concrete can be used in humid climates, but excellent humidity control needs to be established as well.

warm-humid-climate-house-design/
-



Queenslanders they can not build roads or homes, or build a bridge high enough to cross over, But they can be avoided during origin.

From NSW,
Bricks, cement, stones, are permeable, and porous, they will wick up moisture!
Application of damp course can prevent this, or having capping, You need a barrier to prevent this!


 
pollinator
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R-30 Insulation: $4000 Roof + $4000 Floor + $3200 Exterior Walls
AC: $1000 Whole House Dehumidifier +  optional mini-split
Ventilation: $1000 ERV (bathroom always on vent)
Radiant Floor Heating: $1500 PEX piping + $500 Tankless Water Heater + $250 Recirculating Pump + $250 zone Manifold + $10 pressure relief valve

Floor Plan (What do you think of this floor plan? How many rooms did you envision in your head, what about your layout?)


The walkout basement could be used as mirror image 2nd apartment, for guest/renters/workers/airbnb/future grandkids.
The basement could also be used as 3 workshops: A(bedroom1+bedroom2), B(livingroom+kitchen), C (bedroom3+bedroom4)
What do you see yourself using the basement for?
As for humidity in the basement it's the same fix as above, ERV+Dehumidifier+Insulation

Humidity Sources:
Bathroom (vent it, or use outside bathroom)
Kitchen (vent it, or use outside bathroom
Humid Outdoor Air (dehumidify it with AC/dehumidifier/smooth wall earth tube)
 
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the goal is mold avoidance and air quality from what I can gather and not full humidity mitigation per se.

Don't have a sense of your budget.... but...

Were I in similar situation ground infiltration would be a priority concern and ensuring breathable walls rather than air tight.  Breathable walls also starts in the foundation.  Appropriate water diversion, crushed rock, locking wall in footing with external perimeter (internal if necessary) drains.  Using Magnesium based cement as opposed to portland would also be a priority and if steel re-inforcement needed then again- use Portland but minimize its use and use Magnesium layer over the top.  You can also get prefab magboard for flooring and walls.... Cement doesn't have to 'wick' water....But Portland cement certainly does.  Mag is great for avoiding mold.  Fibers/woodchip mixed in mag cements to spread the dollar, increase the overall mass to approach the costs of Portland cement won't necessarily increase mold risk either in the company of Magnesium.  

Insulation wise hemp batting and hempcrete would probably be my priority considerations for mold avoidance along with natural wool, though some natural wool will be treated with chemicals to increase the pest resistance.  These are currently pricey options (the hemp wool wouldn' tbe so bad if not for the shipping as there aren't a lot of places to get it from).  Strawbale shouldn't be avoided for purposes of mold so long as you seal with clay/lime plaster... Testing supports that any potential mold growth does not impact indoor air quality on testing with these methods.  

For any interior wood that doesn't need to be 'shown off' you can paint with nontoxic primer (easier said than able to find)/kaolin clay 50:50 mixture to avoid mold growth.  Not sure how I feel about naturally mold resistant woods as they often are aromatic and have their own natural volatile oils than can be an issue for some people sensitive to chemical irritants (I do love cedar myself.... just don't know about living in it long term).  

You will not escape mold completely from your environment... and sealing all the indoor air pollutants into your home to avoid external mold is probably a worse idea.... so yes, good ventilation and opening windows for an hour a day... and not having any of the core structural materials with some level of permanence being food for mold is generally a good idea....
 
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