It was an ingenious idea. To heat the house, you just had to pull the slider open, the hot air rushes under the bedroom floor and slowly warms the house. To cool down, you push the slider shut and the hot air is blocked and diverted to the chimney leaving the floor beautifully cool. An intake and exhaust stub is built at the very back of the house to be connected to the furnace when built.
She carefully tucked the parchment now covered in charcoal grids mapping out the parallel system against her chest. Carefully, she washed the medical equipment before she took one last look at the unfrozen, rushing spring and turning back. As she rounded the stone rock face, the sheer scale of the construction hit her.
The four colossal ironwood monoliths stood magnificently tall. The workers were cheering, wiping their sweat from their forehead as they packed away the heavy ropes and pulleys. Her husband stood right at the center of the yard, his sleeves rolled up to his elbows despite the biting cold. He was barking a final set of orders to the crew when his eyes caught her.
The sharp commanding edge in his expression hardened instantly. He stepped away from the men and walked over to meet her, the crunching sound of frozen earth sounded.
"You were gone awhile"
His voice mellow and concerned looked carefully at her searching for any sign of fatigue. He noticed the rolled parchment tucked under her arm.
"Did you find what you were looking for?"
"I found something better", she murmured as she unrolled the paper.
Mu Wei was immediately distracted by her mumbling lips and instinctively gulped. Ignoring the burning gaze on her, she continued.
"I found a high pressure spring that won't freeze. And if we dig right now, before the stones are laid, we can run fresh water and subterranean heating flues in the exact same channels".
He leaned in, his sharp gaze tracing the paths she had mapped out. He didn't just see drawings, his tactical mind instantly recognized the logistical brilliance of it. Operating both systems and in a single trench was basically half the labour, double the efficiency and absolute structural safety.
He looked up from the paper, his dark eyes flashing with a mix of deep respect and amusement. Her ideas never failed to amaze him. Building it this way, they never had to worry about the summer or heat as they served both ways.
"You really are trying to build a fortress in this wasteland"
He gently pinched her nose as he murmured. Su Xiao swatted his hands off her face and with a playful tilt of head retorted,
"I'm just trying to make sure we don't freeze to death in winter. So, commander, are you just going to admire my artwork?"
He let out a short, rough laugh his eyes locked on hers with a warmth that had her face flushing.
"We dig"
He led her back to the resting crew. His voice boomed across the camp instantly snapping the men back to attention.
"Alright. Clear the heavy ropes out! Grab your spades and lines. We have work to do. Move!"
The resting crew didn't hesitate. At the command, they grabbed their iron tipped spades and lines up along the lines she quickly began staking out with hemp vines. To the workers, it looked like a maze of chaotic mess, but as they began shovelling, the systematic order of the layout began taking shape.
They didn't just hollow a simple ditch, under her precise supervision, they carved a stripped, terraced trench 4ft deep and 3ft wide into the mountain dirt. The far-right lane plunged the deepest, cutting a full 4ft down into the earth, safely below the mountain's frostline.
The center lane of the trench was terraced slightly higher, at 3ft deep, carved with a meticulous, gradual three-degree upward incline that climbed gently as it traveled from the the front bounds toward the back ridge. Once the gravel foundation was leveled at the bottom of the trenches to prevent shifting, the pipes were systematically lowered.
Down the deep center lane, a team of laborers fitted the interlocking terracotta flue pipes end to end. Every single joint was thickly trapped in a sticky, gas-tight paste of refractory clay mixed with iron fillings, ensuring no smoke could ever leak upward. Running perfectly parallel just six inches to the right, water intake lines were nestled into place.
On the far-left step of the trench, the waste drainage pipes were laid with a sharp, aggressive downward tilt, utilizing pure gravity to ensure gray water would instantly flush far away from the living quarters. She instructed the workers to run the main central terracotta heat pipe through a pre-caved opening beneath the home's exterior stone foundation wall.
It protruded two feet out into the open mountain air, it's mouth temporarily sealed tight with a thick plug of packed clay and dry straw waiting for the furnace to be built. At the opposite end, near the back edge, the exhaust pipe was dangled upward ready to be connected to the chimney when built.
With the pipes successful positioned, the laborers carefully packed the six-inch gap between the heat flue and water line with dense, damp river sand. The sand acted as a perfect regulator to keep the water from freezing and not boiling. Over the top of the centre parallel matrix, the workers dumped baskets of crushed charcoal and ash collected over the few days, tamping it down to create a heavy insulation blanket.
This would force all heat upwards into the house instead of escaping down into freezing earth. Finally, the hidden grid was safely encased in its protective cocoon, the burly workers began rolling the massive, hand-split slate flagstones over the trenches. They aligned them tightly, sealing surface into a smooth, rock-solid floor that locked the entire under-floor system away from sight.
By the time the afternoon sun began to dip behind the mountain peaks, the work had ceased. The workers gathered around having a hearty meal while chatting about today's work. To the workers, it was just a tedious quirk of the rich to want a drainage system. They didn't understand the structural and architectural layout behind it.