Firewood BTU Guide: What to Expect From Colorado Mountain Wood
If you’re searching for firewood BTU comparisons and running across charts full of oak, hickory, and ash — that information isn’t wrong, it’s just not for us. Those are hardwood species. They don’t grow at this elevation in the Southern Rockies. Up here in the San Juans, your firewood comes from what grows here: Engelmann spruce, and some Douglas fir mixed in.
This guide covers the wood species we actually cut and deliver, how their heat output compares, what affects burn quality more than species, and how to figure out how much wood you need for a South Fork winter.
One thing to get out of the way upfront: spruce gets a bad reputation in some firewood guides. Fair enough — green spruce burns terribly. Properly seasoned spruce is a different story. It lights easily, burns consistently, and heats a mountain cabin just fine. That’s what we deliver.
What Is BTU and Why Does It Matter for Firewood?
BTU stands for British Thermal Unit — it’s a measure of heat energy. For firewood, BTU per cord tells you how much total heat a full cord of that species will produce when burned. Higher BTU means more heat per piece of wood, longer burn times, and better coal production.
But BTU ratings assume fully seasoned wood. A freshly cut green piece of any species will burn poorly regardless of its rating, because a significant portion of the energy gets used just boiling off the moisture instead of heating your home.
BTU Comparison: Wood Species in Our Region
Here’s how the species you’ll encounter in the South Fork and Creede area stack up. The grayed-out rows are species we don’t cut or offer — included so you can compare without having to look elsewhere.
| Wood Species | BTU / Cord | Heat Rating | Burn Character | We Carry |
|---|---|---|---|---|
| Engelmann Spruce ★ Our Primary Wood Picea engelmannii | 15.0M BTU per cord | Easy to light, consistent heat, burns clean when properly seasoned. Reliable all-season firewood at elevation. | ✓ Yes | |
| Douglas Fir Mixed In Pseudotsuga menziesii | 20.7M BTU per cord | Denser wood, longer-lasting coals, better for overnight burns. An upgrade when available from current mitigation projects. | ✓ Yes | |
| White Fir Abies concolor | 14.6M BTU per cord | Lower BTU than spruce, pops and sparks more. Not a species we cut. | ✕ No | |
| Aspen Populus tremuloides | 13.5M BTU per cord | Burns fast with minimal coals. Requires significantly more wood for the same heat output. Inferior firewood. | ✕ No | |
| Cottonwood Populus deltoides | 12.1M BTU per cord | Lowest BTU of regional species, retains moisture stubbornly, difficult to season well. Not offered. | ✕ No | |
| Oak (for reference) Quercus spp. | 26.0M BTU per cord | Classic hardwood — listed for comparison only. Does not grow at this elevation in the Southern Rockies. | ✕ No |
BTU figures are approximate per cord (128 cu ft), air-dried to under 20% moisture content. Source: USDA Forest Products Laboratory.
All Timberline firewood is moisture-verified before delivery. Properly seasoned wood at under 20% moisture outperforms any species sold green.
Order Beetle-Kill Firewood →Why No Aspen or Cottonwood?
Aspen and cottonwood grow in this region, but we don’t cut them for firewood — and you shouldn’t buy them from anyone who does. Aspen burns fast and produces almost no coals, which means you’re constantly feeding the fire and getting less heat per dollar. Cottonwood holds moisture stubbornly, takes longer to season properly, and has even lower heat output than aspen.
These are the species that give Colorado wood a bad reputation. We stick to spruce and Douglas fir because they do the job.
Why No Oak or Hardwoods?
If you’ve moved here from the Midwest or Southeast, you may be used to oak, hickory, or ash — hardwoods with excellent BTU ratings. Those species simply don’t grow at elevation in the Southern Rockies. Anyone selling ‘Colorado hardwood’ in this area is either bringing it in from far away at significant cost, or using the term loosely.
Douglas fir is technically classified as a softwood, but it’s denser and higher-BTU than many species commonly called hardwoods. Properly seasoned Douglas fir and spruce heat a mountain home reliably all winter. They’re what’s here. They work.
The Wood We Cut: Engelmann Spruce & Douglas Fir
Engelmann Spruce — The Backbone of Our Supply
Engelmann spruce is what grows up here. It’s also what the spruce beetle has been killing across the Rio Grande National Forest since 1996 — more than 617,000 acres of standing dead timber between South Fork and Creede alone. The wood we cut comes directly from these beetle-kill mitigation projects.
Beetle-killed spruce that’s been standing for a season or two actually has a head start on seasoning. The tree is already dead and drying. Cut it, split it, and stack it properly, and it reaches burnable moisture levels faster than green timber from a live tree.
The distinctive blue-gray streaking you’ll sometimes see in the cross-section is caused by a fungus the beetles carry — sometimes called blue-stain fungus. It’s purely cosmetic. It has no effect on burn quality, BTU output, or how the wood lights. It’s just what beetle-kill spruce looks like, and we think it gives the wood character.
Spruce at 15.0 million BTU per cord burns clean, lights reliably, and holds a fire well through a South Fork winter. It won’t produce the long, slow overnight coals of a hardwood — but it will keep your stove or fireplace running steadily all season.
Douglas Fir — The Upgrade Mixed In
Douglas fir grows alongside spruce at our elevations, and Douglas-fir beetle activity has been increasing in the South Fork–Creede corridor. When mitigation projects include fir, that wood comes into our supply.
At 20.7 million BTU per cord, Douglas fir is notably denser than spruce. It produces better coals, burns longer, and holds heat more steadily — which matters if you’re relying on a wood stove as a primary heat source. Load a stove with Douglas fir in the evening and you’re more likely to have live coals to restart from in the morning.
We don’t always have pure Douglas fir available since supply depends on current mitigation projects. What we can say is that our mixed cords include Douglas fir when it’s available — a meaningful upgrade for no additional cost.
Moisture Content: The Factor That Matters Most
You could buy the highest-BTU firewood in the world. If it’s green, it will burn poorly. Here’s what’s actually happening when you burn wet wood:
- Roughly 25–30% of the energy goes to evaporating moisture before the wood can combust
- The fire burns cooler and produces more smoke from incomplete combustion
- Creosote builds up faster in your flue — a fire hazard requiring expensive cleaning
- The wood hisses, sizzles, and is difficult to keep lit
The industry standard for seasoned firewood is under 20% moisture content. At that level, wood burns cleanly and efficiently. Above 25%, you’re fighting the fire all night.
Every cord we deliver has been verified with a moisture meter. We do not sell wood above 20% moisture content — period. We check it before it goes on the truck.
You can verify moisture content yourself with a pin-type moisture meter ($20–30 at any hardware store). Split a fresh face and test the interior — that’s the accurate reading, not the outer surface.
How Much Firewood Do You Need for a South Fork Winter?
South Fork sits at 8,200 feet elevation. The heating season runs roughly October through April — six to seven months. How much wood you need depends on your heating setup, home size, and how hard you run the fire.
Cord Estimator by Use Case
| Use Case | Supplement / Occasional | Primary Heat Source | Notes |
|---|---|---|---|
| Fireplace Occasional use, ambiance | 1 cord per season | 2–3 cords per season | Evening fires and ambiance. Open fireplaces are less efficient than stoves — plan toward the higher end if it’s your main heat source. |
| Wood Stove Home under 1,500 sq ft | 2–3 cords per season | 4–5 cords per season | South Fork sits at 8,200 ft — heating season runs October through April. A well-insulated cabin uses less; older drafty structures use more. |
| Wood Stove Home 2,500+ sq ft | 3–4 cords per season | 5–8 cords per season | Larger footprint and colder elevation exposure. If you’re relying on wood as the only heat source, plan for the higher end of this range. |
| STR / Vacation Cabin Short-term rental or seasonal use Subscription Available | 2 cords per season | 3–5 cords per season | Guest usage varies widely. Running out mid-season is a guest experience problem. Our STR subscription eliminates that — guaranteed supply, priority scheduling. |
Estimates assume properly seasoned Engelmann spruce or spruce/Douglas fir mix, burned in a typical wood stove or fireplace at elevation. Actual usage varies by insulation, stove efficiency, and burn habits.
Most South Fork homeowners supplementing propane or electric heat use 2–3 cords per winter. Primary-heat households at elevation typically need 4–6.
Order Firewood →These are starting points, not guarantees. A well-insulated modern cabin uses less wood than an older drafty structure. A wood stove with a good firebox insert is more efficient than an open fireplace. If you’re using wood as your primary or only heat source at this elevation, plan toward the higher end.
From what we see delivering in this area: most South Fork homeowners using wood to supplement propane or electric heat use 2–3 cords per winter. Primary-heat households at elevation typically need 4–6 cords.
What Is a Cord? (And What It Isn't)
A cord is a legally defined measurement: 128 cubic feet of stacked wood — 4 feet wide × 4 feet tall × 8 feet long. Not a ‘face cord’ (which is roughly one-third of a cord). Not a ‘truck bed’ (which depends entirely on the truck). Not ‘about a cord.’
If someone can’t tell you exactly how much wood they’re selling, that’s worth noting before you buy. We measure accurately and deliver what we promise. Delivery includes stacking where you need it — covered storage area, woodshed, side of the cabin.
Storing Firewood Properly at Elevation
Even properly seasoned wood can re-absorb moisture if stored poorly. A few practices that matter at our elevation:
- Stack off the ground — use a rack, pallets, or rails. Direct ground contact lets moisture wick up from the soil.
- Cover the top, not the sides — a solid roof or tarp over the top keeps rain and snow off. Wrapping the sides traps humidity and slows drying.
- Allow airflow — stacks should sit where air can move through. Dense shade or a fully enclosed structure keeps moisture levels higher.
- Rotate your supply — burn older wood first. Stack new deliveries behind existing wood and pull from the older stack.
At South Fork elevations, properly stacked seasoned wood holds its moisture content well through a dry mountain winter. A woodshed or good tarp is sufficient.
Frequently Asked Questions
Is spruce good firewood?
Properly seasoned spruce is good firewood — easy to light, consistent heat output, burns clean. The knock on spruce comes from green wood, which burns poorly regardless of species. Beetle-kill spruce that’s been split, stacked, and seasoned to under 20% moisture performs reliably for mountain heating. It’s not oak, but oak doesn’t grow here. For what’s available in the San Juans, spruce is solid.
What is the blue streaking in some firewood pieces?
That blue-gray color is caused by a fungus carried by the spruce beetle — commonly called blue-stain fungus. It doesn’t affect the wood’s burn quality, BTU output, or safety in any way. It’s a cosmetic characteristic of beetle-killed timber. Some people like the look of it in cross-section. It has no effect on how your fire performs.
How long does it take to season firewood?
Freshly cut (green) firewood typically takes 6 to 12 months to season down to usable moisture levels, depending on species, split size, and storage conditions. Beetle-kill spruce that’s been standing dead for a season often seasons faster since the tree started drying before it was cut. We don’t sell green wood — everything we deliver has been moisture-verified and is ready to burn.
Does beetle-kill wood burn the same as live-cut wood?
Yes, once properly seasoned. The beetles killed the tree — they didn’t change the wood’s chemistry or combustion properties. Properly seasoned beetle-kill spruce burns the same as any other properly seasoned spruce. The blue-stain fungus is purely cosmetic and has no effect on burn performance.
Can I order a half cord?
Our minimum order is one full cord. Our delivery model and service area are built around full-cord deliveries — the economics of a half-cord run don’t work well for either of us. If you’re unsure how much you need, call us before you order. We’re happy to talk through it.
Do you deliver to Pagosa Springs or Creede?
Yes. We regularly deliver to South Fork, Creede, and Pagosa Springs. Extended delivery to Del Norte, Monte Vista, and other areas in the region is available — contact us to discuss pricing based on your location.
Order Your Firewood
Order online or call us directly. Delivery typically within 5–7 business days during season. We deliver and stack where you need it.
“The firewood arrived exactly when scheduled, properly seasoned, and stacked where we need it. For our rental property, this reliability is everything, thank you Timberline!”