Home/The Spec
The Styrkholm Spec
Built to a standard you can check.
Most builders sell shelters with adjectives. We publish numbers. Here is how a Styrkholm compound compares with what is commonly sold, and with the standards set by FEMA, the EPA, NFPA and Swiss civil protection.
| System | Commonly sold | The benchmark | The Styrkholm Spec |
|---|---|---|---|
| Structure | Any buried box, often a shipping container | Engineered for soil and groundwater loads | Designed by a licensed engineer for the site's soil, depth and water table, with stamped drawings. No shipping containers. |
| Fresh air per person | Passive vent pipe or small fan | FEMA historic minimum 3 cfm; Oak Ridge guidance about 40 cfm in hot weather | Ventilation sized for hot-weather occupancy at about 40 cfm per person, filtered. |
| Air filtration chain | Filter box on the intake | Swiss shelters: blast valve, pre-filter, blower, NBC filter, overpressure valve, airlock | The complete chain, HEPA plus impregnated carbon, positive pressure, airlock, and a hand-crank backup for the blower. |
| Carbon dioxide | Not addressed | About 1 cfm per person minimum even in cold weather | Continuous CO2 monitoring with alarm in every occupied below-grade room. |
| Radiation shielding | Unstated | Each 2.2 in. of concrete or 3.3 in. of packed earth roughly halves gamma radiation | Sleeping and living quarters designed for a protection factor of about 1,000, roughly ten halving thicknesses of mass. |
| Radon | Not mentioned | EPA action level 4 pCi/L; consider fixing from 2 pCi/L | Sub-slab mitigation built in, with every below-grade space tested after occupancy and brought below 2 pCi/L. |
| Moisture | Waterproof coating | Ground holds about 40 to 70°F year round, so condensation is the common failure | Membrane waterproofing, perimeter drainage and dehumidification sized for full occupancy. |
| Water | A few cases of bottled water | Ready.gov: 1 gallon per person per day for at least 3 days | A permanent source with secured water rights, off-grid pumping and treatment, plus stored reserve for the full 180 days at minimum use. |
| Backup fuel | A generator and a full tank | NFPA 110: fuel-quality test at least annually; diesel about 6 to 12 months | Propane where long storage matters; diesel tested and treated on an NFPA 110 schedule, with tank capacity tied to days of runtime. |
| Batteries | Wherever they fit | Lithium must not be charged below 32°F | Battery banks in conditioned or below-grade rooms that stay above freezing, with low-temperature charge protection. |
| Food storage | Shelves in the garage | BYU: wheat and rice acceptable after 30+ years sealed without oxygen at room temperature or below | A cool, dark, dry storage vault below grade, held steady year round, with rotation shelving and a root cellar. |
| Safe room | "Reinforced" closet | FEMA P-361 and ICC 500: 250 mph wind, 15 lb 2x4 at 100 mph | Safe rooms in the residence built to FEMA P-361. |
| Duration | 72 hours | U.S. bases: 90 days reported planning goal | The 180-day standard: a full winter with no deliveries, utilities or outside services. |
Design targets. Every Styrkholm compound is engineered by licensed professionals for its site and household, and final specifications are set in writing during design. Benchmarks are summarized from the sources below.
- Nuclear War Survival Skills (Oak Ridge National Laboratory), Ch. 7: Ventilation and cooling
- Swiss Federal Office for Civil Protection: Shelters for the population
- U.S. EPA: Health risks of radon (archived)
- Ready.gov: Water (archived)
- Clean fuel for generators: a drill-down of NFPA 110
- REDARC: Why you should not charge a lithium battery below 0°C / 32°F
- FLASH: FEMA P-361 and ICC 500 safe rooms
- U.S. Department of Energy: Geothermal heat pumps
- BYU Magazine: Ask an expert, new tips for old food
- DHS Center for Domestic Preparedness: the 7:10 rule of thumb
Questions
About
the Spec.
Are these specifications guaranteed for every project?
They are Styrkholm's design targets. Every compound is engineered by licensed professionals for its own site, soil, climate and household, and the final specifications are set in writing during design.
Why publish our standards?
Because the industry rarely does. Buyers should be able to compare builders on numbers: air per person, protection factor, radon levels, days of water and fuel. We would rather be measured than trusted.
Where do the benchmarks come from?
Swiss civil protection, FEMA, the EPA, NFPA 110, the U.S. Department of Energy, Ready.gov, Oak Ridge National Laboratory's shelter research and BYU's food storage research. Each is linked below.
Hold us to it.
Bring this page to your consultation. We will show you how each number is met on your land.